From 366e0d87402540bb627e36fd42fefd63030c5491 Mon Sep 17 00:00:00 2001
From: Masafumi Koba <473530+ybiquitous@users.noreply.github.com>
Date: Mon, 3 Jul 2023 09:11:53 +0900
Subject: [PATCH 1/2] Switch Jest `coverageProvider` from `babel` (default) to
 `v8` (#7025)

Ref:
- https://jestjs.io/docs/29.0/configuration#coverageprovider-string
- https://jestjs.io/blog/2020/01/21/jest-25#v8-code-coverage
---
 package.json | 1 +
 1 file changed, 1 insertion(+)

diff --git a/package.json b/package.json
index 5fb9a5fe0a..4ef3a5e404 100644
--- a/package.json
+++ b/package.json
@@ -100,6 +100,7 @@
       "!lib/**/{__tests__,testUtils}/**/*.{js,mjs}"
     ],
     "coverageDirectory": "./.coverage/",
+    "coverageProvider": "v8",
     "coverageReporters": [
       "lcov",
       "text-summary"

From b919a0b7c804ad9bcc318f41dc90111ddbd6b9f4 Mon Sep 17 00:00:00 2001
From: Masafumi Koba <473530+ybiquitous@users.noreply.github.com>
Date: Mon, 3 Jul 2023 09:27:43 +0900
Subject: [PATCH 2/2] Refactor `lib/rules/__tests__/*` test files to migrate to
 ESM (#7024)

This change is performed by the following script (though it requires a bit of manual).

```shell
node to-esm.mjs lib/rules/*/__tests__/index.js
```

```js
// to-esm.mjs
import { argv, stdout } from 'node:process';
import { readFile, unlink, writeFile } from 'node:fs/promises';
import { execSync } from 'node:child_process';

async function processFile(file) {
	const ruleFile = file.replace('/__tests__/index.js', '/index.js');

	if ((await readFile(ruleFile, 'utf8')).includes('\tdeprecated: true,')) {
		stdout.write(`Skip deprecated ${file}\n`);

		return;
	}

	let lines = (await readFile(file, 'utf8')).split('\n');

	lines = lines.filter((line) => !line.includes('use strict'));

	lines.forEach((line, i) => {
		line = line.replace(
			"const stripIndent = require('common-tags').stripIndent",
			"const { stripIndent } = require('common-tags')",
		);

		line = line.replace(
			"const { messages, ruleName } = require('..');",
			"import rule from '../index.js'; const { messages, ruleName } = rule;",
		);

		line = line.replace(/const (.+) = require\('(\..+)'\)/, 'import $1 from "$2.js"');
		line = line.replace(/const (.+) = require\('(.+)'\)/, 'import $1 from "$2"');

		lines[i] = line;
	});

	const newFile = file.replace(/\.js$/, '.mjs');
	const newContent = `${lines.join('\n')}\n`;

	await writeFile(newFile, newContent);

	stdout.write(`=> ${newFile}\n`);

	await unlink(file);
}

const files = argv.slice(2);

Promise.all(files.map((f) => processFile(f))).then(() => {
	execSync(`npx prettier --loglevel silent --write lib/rules`, { encoding: 'utf8' });
});
```
---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  9 ++++-----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  9 ++++-----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
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 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  9 ++++-----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
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 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  6 +++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
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 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  6 +++---
 .../__tests__/{index.js => index.mjs}            |  9 ++++-----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            | 16 +++++++---------
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
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 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
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 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
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 .../__tests__/{index.js => index.mjs}            |  5 ++---
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 .../__tests__/{index.js => index.mjs}            |  5 ++---
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 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  7 +++----
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
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 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 .../__tests__/{index.js => index.mjs}            |  5 ++---
 125 files changed, 289 insertions(+), 413 deletions(-)
 rename lib/rules/alpha-value-notation/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/annotation-no-unknown/__tests__/{index.js => index.mjs} (93%)
 rename lib/rules/at-rule-allowed-list/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/at-rule-disallowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/at-rule-empty-line-before/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/at-rule-no-unknown/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/at-rule-no-vendor-prefix/__tests__/{index.js => index.mjs} (94%)
 rename lib/rules/at-rule-property-required-list/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/block-no-empty/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/color-function-notation/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/color-hex-alpha/__tests__/{index.js => index.mjs} (95%)
 rename lib/rules/color-hex-length/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/color-named/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/color-no-hex/__tests__/{index.js => index.mjs} (94%)
 rename lib/rules/color-no-invalid-hex/__tests__/{index.js => index.mjs} (94%)
 rename lib/rules/comment-empty-line-before/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/comment-no-empty/__tests__/{index.js => index.mjs} (93%)
 rename lib/rules/comment-pattern/__tests__/{index.js => index.mjs} (92%)
 rename lib/rules/comment-whitespace-inside/__tests__/{index.js => index.mjs} (98%)
 mode change 100755 => 100644
 rename lib/rules/comment-word-disallowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/custom-media-pattern/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/custom-property-empty-line-before/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/custom-property-no-missing-var-function/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/custom-property-pattern/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/declaration-block-no-duplicate-custom-properties/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/declaration-block-no-duplicate-properties/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/declaration-block-no-redundant-longhand-properties/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/declaration-block-no-shorthand-property-overrides/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/declaration-block-single-line-max-declarations/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/declaration-empty-line-before/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/declaration-no-important/__tests__/{index.js => index.mjs} (90%)
 rename lib/rules/declaration-property-max-values/__tests__/{index.js => index.mjs} (95%)
 rename lib/rules/declaration-property-unit-allowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/declaration-property-unit-disallowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/declaration-property-value-allowed-list/__tests__/{index.js => index.mjs} (95%)
 rename lib/rules/declaration-property-value-disallowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/declaration-property-value-no-unknown/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/font-family-name-quotes/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/font-family-no-duplicate-names/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/font-family-no-missing-generic-family-keyword/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/font-weight-notation/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/function-allowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/function-calc-no-unspaced-operator/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/function-disallowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/function-linear-gradient-no-nonstandard-direction/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/function-name-case/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/function-no-unknown/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/function-url-no-scheme-relative/__tests__/{index.js => index.mjs} (95%)
 rename lib/rules/function-url-quotes/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/function-url-scheme-allowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/function-url-scheme-disallowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/hue-degree-notation/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/import-notation/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/keyframe-block-no-duplicate-selectors/__tests__/{index.js => index.mjs} (94%)
 rename lib/rules/keyframe-declaration-no-important/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/keyframe-selector-notation/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/keyframes-name-pattern/__tests__/{index.js => index.mjs} (95%)
 rename lib/rules/length-zero-no-unit/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/max-nesting-depth/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/media-feature-name-allowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/media-feature-name-disallowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/media-feature-name-no-unknown/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/media-feature-name-no-vendor-prefix/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/media-feature-name-unit-allowed-list/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/media-feature-name-value-allowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/media-feature-name-value-no-unknown/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/media-feature-range-notation/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/media-query-no-invalid/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/named-grid-areas-no-invalid/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/no-descending-specificity/__tests__/{index.js => index.mjs} (95%)
 rename lib/rules/no-duplicate-at-import-rules/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/no-duplicate-selectors/__tests__/{index.js => index.mjs} (94%)
 rename lib/rules/no-empty-source/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/no-invalid-double-slash-comments/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/no-invalid-position-at-import-rule/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/no-irregular-whitespace/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/no-unknown-animations/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/no-unknown-custom-properties/__tests__/{index.js => index.mjs} (93%)
 rename lib/rules/number-max-precision/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/property-allowed-list/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/property-disallowed-list/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/property-no-unknown/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/property-no-vendor-prefix/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/rule-empty-line-before/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/rule-selector-property-disallowed-list/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/selector-anb-no-unmatchable/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/selector-attribute-name-disallowed-list/__tests__/{index.js => index.mjs} (95%)
 rename lib/rules/selector-attribute-operator-allowed-list/__tests__/{index.js => index.mjs} (95%)
 rename lib/rules/selector-attribute-operator-disallowed-list/__tests__/{index.js => index.mjs} (95%)
 rename lib/rules/selector-attribute-quotes/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/selector-class-pattern/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/selector-combinator-allowed-list/__tests__/{index.js => index.mjs} (94%)
 rename lib/rules/selector-combinator-disallowed-list/__tests__/{index.js => index.mjs} (94%)
 rename lib/rules/selector-disallowed-list/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/selector-id-pattern/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/selector-max-attribute/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/selector-max-class/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/selector-max-combinators/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/selector-max-compound-selectors/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/selector-max-id/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/selector-max-pseudo-class/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/selector-max-specificity/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/selector-max-type/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/selector-max-universal/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/selector-nested-pattern/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/selector-no-qualifying-type/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/selector-no-vendor-prefix/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/selector-not-notation/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/selector-pseudo-class-allowed-list/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/selector-pseudo-class-disallowed-list/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/selector-pseudo-class-no-unknown/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/selector-pseudo-element-allowed-list/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/selector-pseudo-element-colon-notation/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/selector-pseudo-element-disallowed-list/__tests__/{index.js => index.mjs} (96%)
 rename lib/rules/selector-pseudo-element-no-unknown/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/selector-type-case/__tests__/{index.js => index.mjs} (98%)
 rename lib/rules/selector-type-no-unknown/__tests__/{index.js => index.mjs} (97%)
 rename lib/rules/shorthand-property-no-redundant-values/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/string-no-newline/__tests__/{index.js => index.mjs} (95%)
 rename lib/rules/time-min-milliseconds/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/unit-allowed-list/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/unit-disallowed-list/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/unit-no-unknown/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/value-keyword-case/__tests__/{index.js => index.mjs} (99%)
 rename lib/rules/value-no-vendor-prefix/__tests__/{index.js => index.mjs} (98%)

diff --git a/lib/rules/alpha-value-notation/__tests__/index.js b/lib/rules/alpha-value-notation/__tests__/index.mjs
similarity index 98%
rename from lib/rules/alpha-value-notation/__tests__/index.js
rename to lib/rules/alpha-value-notation/__tests__/index.mjs
index 73cc861eba..6e1aac481c 100644
--- a/lib/rules/alpha-value-notation/__tests__/index.js
+++ b/lib/rules/alpha-value-notation/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const stripIndent = require('common-tags').stripIndent;
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/annotation-no-unknown/__tests__/index.js b/lib/rules/annotation-no-unknown/__tests__/index.mjs
similarity index 93%
rename from lib/rules/annotation-no-unknown/__tests__/index.js
rename to lib/rules/annotation-no-unknown/__tests__/index.mjs
index 3ec8513f0f..e5630038ac 100644
--- a/lib/rules/annotation-no-unknown/__tests__/index.js
+++ b/lib/rules/annotation-no-unknown/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/at-rule-allowed-list/__tests__/index.js b/lib/rules/at-rule-allowed-list/__tests__/index.mjs
similarity index 97%
rename from lib/rules/at-rule-allowed-list/__tests__/index.js
rename to lib/rules/at-rule-allowed-list/__tests__/index.mjs
index 8e720e9f74..85196aaf1d 100644
--- a/lib/rules/at-rule-allowed-list/__tests__/index.js
+++ b/lib/rules/at-rule-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/at-rule-disallowed-list/__tests__/index.js b/lib/rules/at-rule-disallowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/at-rule-disallowed-list/__tests__/index.js
rename to lib/rules/at-rule-disallowed-list/__tests__/index.mjs
index 5d3f0f0474..246edc439e 100644
--- a/lib/rules/at-rule-disallowed-list/__tests__/index.js
+++ b/lib/rules/at-rule-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/at-rule-empty-line-before/__tests__/index.js b/lib/rules/at-rule-empty-line-before/__tests__/index.mjs
similarity index 99%
rename from lib/rules/at-rule-empty-line-before/__tests__/index.js
rename to lib/rules/at-rule-empty-line-before/__tests__/index.mjs
index b811aba78f..c02a26d344 100644
--- a/lib/rules/at-rule-empty-line-before/__tests__/index.js
+++ b/lib/rules/at-rule-empty-line-before/__tests__/index.mjs
@@ -1,9 +1,8 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const stripIndent = require('common-tags').stripIndent;
-
-const mergeTestDescriptions = require('../../../testUtils/mergeTestDescriptions');
-const { messages, ruleName } = require('..');
+import mergeTestDescriptions from '../../../testUtils/mergeTestDescriptions.js';
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 const sharedAlwaysTests = {
 	accept: [
diff --git a/lib/rules/at-rule-no-unknown/__tests__/index.js b/lib/rules/at-rule-no-unknown/__tests__/index.mjs
similarity index 98%
rename from lib/rules/at-rule-no-unknown/__tests__/index.js
rename to lib/rules/at-rule-no-unknown/__tests__/index.mjs
index abc72bcf37..b7913fd486 100644
--- a/lib/rules/at-rule-no-unknown/__tests__/index.js
+++ b/lib/rules/at-rule-no-unknown/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/at-rule-no-vendor-prefix/__tests__/index.js b/lib/rules/at-rule-no-vendor-prefix/__tests__/index.mjs
similarity index 94%
rename from lib/rules/at-rule-no-vendor-prefix/__tests__/index.js
rename to lib/rules/at-rule-no-vendor-prefix/__tests__/index.mjs
index 94d54cf70e..bddd9c0698 100644
--- a/lib/rules/at-rule-no-vendor-prefix/__tests__/index.js
+++ b/lib/rules/at-rule-no-vendor-prefix/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/at-rule-property-required-list/__tests__/index.js b/lib/rules/at-rule-property-required-list/__tests__/index.mjs
similarity index 96%
rename from lib/rules/at-rule-property-required-list/__tests__/index.js
rename to lib/rules/at-rule-property-required-list/__tests__/index.mjs
index 5d1c833456..23b4533d35 100644
--- a/lib/rules/at-rule-property-required-list/__tests__/index.js
+++ b/lib/rules/at-rule-property-required-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/block-no-empty/__tests__/index.js b/lib/rules/block-no-empty/__tests__/index.mjs
similarity index 98%
rename from lib/rules/block-no-empty/__tests__/index.js
rename to lib/rules/block-no-empty/__tests__/index.mjs
index 91aa0ffe35..bd2e0285f9 100644
--- a/lib/rules/block-no-empty/__tests__/index.js
+++ b/lib/rules/block-no-empty/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/color-function-notation/__tests__/index.js b/lib/rules/color-function-notation/__tests__/index.mjs
similarity index 98%
rename from lib/rules/color-function-notation/__tests__/index.js
rename to lib/rules/color-function-notation/__tests__/index.mjs
index 2a21b68935..f18d5342ed 100644
--- a/lib/rules/color-function-notation/__tests__/index.js
+++ b/lib/rules/color-function-notation/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const stripIndent = require('common-tags').stripIndent;
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/color-hex-alpha/__tests__/index.js b/lib/rules/color-hex-alpha/__tests__/index.mjs
similarity index 95%
rename from lib/rules/color-hex-alpha/__tests__/index.js
rename to lib/rules/color-hex-alpha/__tests__/index.mjs
index 05236fb4ab..858a5813cc 100644
--- a/lib/rules/color-hex-alpha/__tests__/index.js
+++ b/lib/rules/color-hex-alpha/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/color-hex-length/__tests__/index.js b/lib/rules/color-hex-length/__tests__/index.mjs
similarity index 96%
rename from lib/rules/color-hex-length/__tests__/index.js
rename to lib/rules/color-hex-length/__tests__/index.mjs
index 1d266ee22d..6f4f0799bd 100644
--- a/lib/rules/color-hex-length/__tests__/index.js
+++ b/lib/rules/color-hex-length/__tests__/index.mjs
@@ -1,9 +1,8 @@
-'use strict';
+import mergeTestDescriptions from '../../../testUtils/mergeTestDescriptions.js';
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-const mergeTestDescriptions = require('../../../testUtils/mergeTestDescriptions');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 const sharedTests = {
 	accept: [
diff --git a/lib/rules/color-named/__tests__/index.js b/lib/rules/color-named/__tests__/index.mjs
similarity index 99%
rename from lib/rules/color-named/__tests__/index.js
rename to lib/rules/color-named/__tests__/index.mjs
index a7f42f0627..c3872246f7 100644
--- a/lib/rules/color-named/__tests__/index.js
+++ b/lib/rules/color-named/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/color-no-hex/__tests__/index.js b/lib/rules/color-no-hex/__tests__/index.mjs
similarity index 94%
rename from lib/rules/color-no-hex/__tests__/index.js
rename to lib/rules/color-no-hex/__tests__/index.mjs
index 4f1cfc2e74..9d4291c187 100644
--- a/lib/rules/color-no-hex/__tests__/index.js
+++ b/lib/rules/color-no-hex/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/color-no-invalid-hex/__tests__/index.js b/lib/rules/color-no-invalid-hex/__tests__/index.mjs
similarity index 94%
rename from lib/rules/color-no-invalid-hex/__tests__/index.js
rename to lib/rules/color-no-invalid-hex/__tests__/index.mjs
index 1f2779db1e..e18879bea8 100644
--- a/lib/rules/color-no-invalid-hex/__tests__/index.js
+++ b/lib/rules/color-no-invalid-hex/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/comment-empty-line-before/__tests__/index.js b/lib/rules/comment-empty-line-before/__tests__/index.mjs
similarity index 97%
rename from lib/rules/comment-empty-line-before/__tests__/index.js
rename to lib/rules/comment-empty-line-before/__tests__/index.mjs
index e4b5c0c27f..9cd31f3d68 100644
--- a/lib/rules/comment-empty-line-before/__tests__/index.js
+++ b/lib/rules/comment-empty-line-before/__tests__/index.mjs
@@ -1,7 +1,6 @@
-'use strict';
-
-const mergeTestDescriptions = require('../../../testUtils/mergeTestDescriptions');
-const { messages, ruleName } = require('..');
+import mergeTestDescriptions from '../../../testUtils/mergeTestDescriptions.js';
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 const alwaysTests = {
 	accept: [
diff --git a/lib/rules/comment-no-empty/__tests__/index.js b/lib/rules/comment-no-empty/__tests__/index.mjs
similarity index 93%
rename from lib/rules/comment-no-empty/__tests__/index.js
rename to lib/rules/comment-no-empty/__tests__/index.mjs
index 3b6b313661..72d681908d 100644
--- a/lib/rules/comment-no-empty/__tests__/index.js
+++ b/lib/rules/comment-no-empty/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/comment-pattern/__tests__/index.js b/lib/rules/comment-pattern/__tests__/index.mjs
similarity index 92%
rename from lib/rules/comment-pattern/__tests__/index.js
rename to lib/rules/comment-pattern/__tests__/index.mjs
index a924320830..53ec105fb3 100644
--- a/lib/rules/comment-pattern/__tests__/index.js
+++ b/lib/rules/comment-pattern/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const { stripIndent } = require('common-tags');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/comment-whitespace-inside/__tests__/index.js b/lib/rules/comment-whitespace-inside/__tests__/index.mjs
old mode 100755
new mode 100644
similarity index 98%
rename from lib/rules/comment-whitespace-inside/__tests__/index.js
rename to lib/rules/comment-whitespace-inside/__tests__/index.mjs
index e415fe5ba6..361cfa8d54
--- a/lib/rules/comment-whitespace-inside/__tests__/index.js
+++ b/lib/rules/comment-whitespace-inside/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/comment-word-disallowed-list/__tests__/index.js b/lib/rules/comment-word-disallowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/comment-word-disallowed-list/__tests__/index.js
rename to lib/rules/comment-word-disallowed-list/__tests__/index.mjs
index 08f2e70ad9..f6f139da31 100644
--- a/lib/rules/comment-word-disallowed-list/__tests__/index.js
+++ b/lib/rules/comment-word-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/custom-media-pattern/__tests__/index.js b/lib/rules/custom-media-pattern/__tests__/index.mjs
similarity index 97%
rename from lib/rules/custom-media-pattern/__tests__/index.js
rename to lib/rules/custom-media-pattern/__tests__/index.mjs
index ce36db7bf0..92d3612e87 100644
--- a/lib/rules/custom-media-pattern/__tests__/index.js
+++ b/lib/rules/custom-media-pattern/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/custom-property-empty-line-before/__tests__/index.js b/lib/rules/custom-property-empty-line-before/__tests__/index.mjs
similarity index 98%
rename from lib/rules/custom-property-empty-line-before/__tests__/index.js
rename to lib/rules/custom-property-empty-line-before/__tests__/index.mjs
index 91de21b81a..b49de79050 100644
--- a/lib/rules/custom-property-empty-line-before/__tests__/index.js
+++ b/lib/rules/custom-property-empty-line-before/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/custom-property-no-missing-var-function/__tests__/index.js b/lib/rules/custom-property-no-missing-var-function/__tests__/index.mjs
similarity index 96%
rename from lib/rules/custom-property-no-missing-var-function/__tests__/index.js
rename to lib/rules/custom-property-no-missing-var-function/__tests__/index.mjs
index 400edf1673..77c29c724f 100644
--- a/lib/rules/custom-property-no-missing-var-function/__tests__/index.js
+++ b/lib/rules/custom-property-no-missing-var-function/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const stripIndent = require('common-tags').stripIndent;
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/custom-property-pattern/__tests__/index.js b/lib/rules/custom-property-pattern/__tests__/index.mjs
similarity index 97%
rename from lib/rules/custom-property-pattern/__tests__/index.js
rename to lib/rules/custom-property-pattern/__tests__/index.mjs
index 02073b10cd..2e6e97b70b 100644
--- a/lib/rules/custom-property-pattern/__tests__/index.js
+++ b/lib/rules/custom-property-pattern/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-block-no-duplicate-custom-properties/__tests__/index.js b/lib/rules/declaration-block-no-duplicate-custom-properties/__tests__/index.mjs
similarity index 97%
rename from lib/rules/declaration-block-no-duplicate-custom-properties/__tests__/index.js
rename to lib/rules/declaration-block-no-duplicate-custom-properties/__tests__/index.mjs
index 3cb28543f9..9d6f548ba9 100644
--- a/lib/rules/declaration-block-no-duplicate-custom-properties/__tests__/index.js
+++ b/lib/rules/declaration-block-no-duplicate-custom-properties/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-block-no-duplicate-properties/__tests__/index.js b/lib/rules/declaration-block-no-duplicate-properties/__tests__/index.mjs
similarity index 99%
rename from lib/rules/declaration-block-no-duplicate-properties/__tests__/index.js
rename to lib/rules/declaration-block-no-duplicate-properties/__tests__/index.mjs
index b0bacd64f3..c8ccc0d3af 100644
--- a/lib/rules/declaration-block-no-duplicate-properties/__tests__/index.js
+++ b/lib/rules/declaration-block-no-duplicate-properties/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-block-no-redundant-longhand-properties/__tests__/index.js b/lib/rules/declaration-block-no-redundant-longhand-properties/__tests__/index.mjs
similarity index 98%
rename from lib/rules/declaration-block-no-redundant-longhand-properties/__tests__/index.js
rename to lib/rules/declaration-block-no-redundant-longhand-properties/__tests__/index.mjs
index 7b77d3e305..29e4d6444e 100644
--- a/lib/rules/declaration-block-no-redundant-longhand-properties/__tests__/index.js
+++ b/lib/rules/declaration-block-no-redundant-longhand-properties/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-block-no-shorthand-property-overrides/__tests__/index.js b/lib/rules/declaration-block-no-shorthand-property-overrides/__tests__/index.mjs
similarity index 96%
rename from lib/rules/declaration-block-no-shorthand-property-overrides/__tests__/index.js
rename to lib/rules/declaration-block-no-shorthand-property-overrides/__tests__/index.mjs
index 8543e11fce..c59937ab7f 100644
--- a/lib/rules/declaration-block-no-shorthand-property-overrides/__tests__/index.js
+++ b/lib/rules/declaration-block-no-shorthand-property-overrides/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-block-single-line-max-declarations/__tests__/index.js b/lib/rules/declaration-block-single-line-max-declarations/__tests__/index.mjs
similarity index 96%
rename from lib/rules/declaration-block-single-line-max-declarations/__tests__/index.js
rename to lib/rules/declaration-block-single-line-max-declarations/__tests__/index.mjs
index 90c627d2a8..798835b87d 100644
--- a/lib/rules/declaration-block-single-line-max-declarations/__tests__/index.js
+++ b/lib/rules/declaration-block-single-line-max-declarations/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-empty-line-before/__tests__/index.js b/lib/rules/declaration-empty-line-before/__tests__/index.mjs
similarity index 99%
rename from lib/rules/declaration-empty-line-before/__tests__/index.js
rename to lib/rules/declaration-empty-line-before/__tests__/index.mjs
index dc298e89b8..6b12e968d7 100644
--- a/lib/rules/declaration-empty-line-before/__tests__/index.js
+++ b/lib/rules/declaration-empty-line-before/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const stripIndent = require('common-tags').stripIndent;
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-no-important/__tests__/index.js b/lib/rules/declaration-no-important/__tests__/index.mjs
similarity index 90%
rename from lib/rules/declaration-no-important/__tests__/index.js
rename to lib/rules/declaration-no-important/__tests__/index.mjs
index 09145b3757..e51836d3fa 100644
--- a/lib/rules/declaration-no-important/__tests__/index.js
+++ b/lib/rules/declaration-no-important/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-property-max-values/__tests__/index.js b/lib/rules/declaration-property-max-values/__tests__/index.mjs
similarity index 95%
rename from lib/rules/declaration-property-max-values/__tests__/index.js
rename to lib/rules/declaration-property-max-values/__tests__/index.mjs
index 60ad871054..80404bdd89 100644
--- a/lib/rules/declaration-property-max-values/__tests__/index.js
+++ b/lib/rules/declaration-property-max-values/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-property-unit-allowed-list/__tests__/index.js b/lib/rules/declaration-property-unit-allowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/declaration-property-unit-allowed-list/__tests__/index.js
rename to lib/rules/declaration-property-unit-allowed-list/__tests__/index.mjs
index 32ff7d11de..75da0d956f 100644
--- a/lib/rules/declaration-property-unit-allowed-list/__tests__/index.js
+++ b/lib/rules/declaration-property-unit-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-property-unit-disallowed-list/__tests__/index.js b/lib/rules/declaration-property-unit-disallowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/declaration-property-unit-disallowed-list/__tests__/index.js
rename to lib/rules/declaration-property-unit-disallowed-list/__tests__/index.mjs
index 4d19329b94..f84e60b097 100644
--- a/lib/rules/declaration-property-unit-disallowed-list/__tests__/index.js
+++ b/lib/rules/declaration-property-unit-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-property-value-allowed-list/__tests__/index.js b/lib/rules/declaration-property-value-allowed-list/__tests__/index.mjs
similarity index 95%
rename from lib/rules/declaration-property-value-allowed-list/__tests__/index.js
rename to lib/rules/declaration-property-value-allowed-list/__tests__/index.mjs
index 16ce488ef9..09c1f32afa 100644
--- a/lib/rules/declaration-property-value-allowed-list/__tests__/index.js
+++ b/lib/rules/declaration-property-value-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-property-value-disallowed-list/__tests__/index.js b/lib/rules/declaration-property-value-disallowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/declaration-property-value-disallowed-list/__tests__/index.js
rename to lib/rules/declaration-property-value-disallowed-list/__tests__/index.mjs
index 99a62cbb5b..90a1ba0f07 100644
--- a/lib/rules/declaration-property-value-disallowed-list/__tests__/index.js
+++ b/lib/rules/declaration-property-value-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/declaration-property-value-no-unknown/__tests__/index.js b/lib/rules/declaration-property-value-no-unknown/__tests__/index.mjs
similarity index 98%
rename from lib/rules/declaration-property-value-no-unknown/__tests__/index.js
rename to lib/rules/declaration-property-value-no-unknown/__tests__/index.mjs
index da839a02f8..83dd0d19ea 100644
--- a/lib/rules/declaration-property-value-no-unknown/__tests__/index.js
+++ b/lib/rules/declaration-property-value-no-unknown/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/font-family-name-quotes/__tests__/index.js b/lib/rules/font-family-name-quotes/__tests__/index.mjs
similarity index 99%
rename from lib/rules/font-family-name-quotes/__tests__/index.js
rename to lib/rules/font-family-name-quotes/__tests__/index.mjs
index 648fa45e13..c16c38ea9b 100644
--- a/lib/rules/font-family-name-quotes/__tests__/index.js
+++ b/lib/rules/font-family-name-quotes/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 const variablePositiveTests = [
 	{
diff --git a/lib/rules/font-family-no-duplicate-names/__tests__/index.js b/lib/rules/font-family-no-duplicate-names/__tests__/index.mjs
similarity index 97%
rename from lib/rules/font-family-no-duplicate-names/__tests__/index.js
rename to lib/rules/font-family-no-duplicate-names/__tests__/index.mjs
index f1a3848073..77fa059613 100644
--- a/lib/rules/font-family-no-duplicate-names/__tests__/index.js
+++ b/lib/rules/font-family-no-duplicate-names/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/font-family-no-missing-generic-family-keyword/__tests__/index.js b/lib/rules/font-family-no-missing-generic-family-keyword/__tests__/index.mjs
similarity index 98%
rename from lib/rules/font-family-no-missing-generic-family-keyword/__tests__/index.js
rename to lib/rules/font-family-no-missing-generic-family-keyword/__tests__/index.mjs
index 9f1d6598bf..851e23986e 100644
--- a/lib/rules/font-family-no-missing-generic-family-keyword/__tests__/index.js
+++ b/lib/rules/font-family-no-missing-generic-family-keyword/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/font-weight-notation/__tests__/index.js b/lib/rules/font-weight-notation/__tests__/index.mjs
similarity index 99%
rename from lib/rules/font-weight-notation/__tests__/index.js
rename to lib/rules/font-weight-notation/__tests__/index.mjs
index 686670b83a..6b3e2bf6b7 100644
--- a/lib/rules/font-weight-notation/__tests__/index.js
+++ b/lib/rules/font-weight-notation/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/function-allowed-list/__tests__/index.js b/lib/rules/function-allowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/function-allowed-list/__tests__/index.js
rename to lib/rules/function-allowed-list/__tests__/index.mjs
index dcca9b57ed..d2b12b00e6 100644
--- a/lib/rules/function-allowed-list/__tests__/index.js
+++ b/lib/rules/function-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/function-calc-no-unspaced-operator/__tests__/index.js b/lib/rules/function-calc-no-unspaced-operator/__tests__/index.mjs
similarity index 99%
rename from lib/rules/function-calc-no-unspaced-operator/__tests__/index.js
rename to lib/rules/function-calc-no-unspaced-operator/__tests__/index.mjs
index bfa1a6feb8..03b02128e6 100644
--- a/lib/rules/function-calc-no-unspaced-operator/__tests__/index.js
+++ b/lib/rules/function-calc-no-unspaced-operator/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/function-disallowed-list/__tests__/index.js b/lib/rules/function-disallowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/function-disallowed-list/__tests__/index.js
rename to lib/rules/function-disallowed-list/__tests__/index.mjs
index 1ef3fdbd87..4ebc2bc995 100644
--- a/lib/rules/function-disallowed-list/__tests__/index.js
+++ b/lib/rules/function-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/function-linear-gradient-no-nonstandard-direction/__tests__/index.js b/lib/rules/function-linear-gradient-no-nonstandard-direction/__tests__/index.mjs
similarity index 99%
rename from lib/rules/function-linear-gradient-no-nonstandard-direction/__tests__/index.js
rename to lib/rules/function-linear-gradient-no-nonstandard-direction/__tests__/index.mjs
index 97bbf2ded0..8a0a517218 100644
--- a/lib/rules/function-linear-gradient-no-nonstandard-direction/__tests__/index.js
+++ b/lib/rules/function-linear-gradient-no-nonstandard-direction/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/function-name-case/__tests__/index.js b/lib/rules/function-name-case/__tests__/index.mjs
similarity index 99%
rename from lib/rules/function-name-case/__tests__/index.js
rename to lib/rules/function-name-case/__tests__/index.mjs
index 5a7e02aff7..cc9957b6c2 100644
--- a/lib/rules/function-name-case/__tests__/index.js
+++ b/lib/rules/function-name-case/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/function-no-unknown/__tests__/index.js b/lib/rules/function-no-unknown/__tests__/index.mjs
similarity index 96%
rename from lib/rules/function-no-unknown/__tests__/index.js
rename to lib/rules/function-no-unknown/__tests__/index.mjs
index a0a9d5cacf..c15745edbd 100644
--- a/lib/rules/function-no-unknown/__tests__/index.js
+++ b/lib/rules/function-no-unknown/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/function-url-no-scheme-relative/__tests__/index.js b/lib/rules/function-url-no-scheme-relative/__tests__/index.mjs
similarity index 95%
rename from lib/rules/function-url-no-scheme-relative/__tests__/index.js
rename to lib/rules/function-url-no-scheme-relative/__tests__/index.mjs
index dadfb4e8af..3c86391890 100644
--- a/lib/rules/function-url-no-scheme-relative/__tests__/index.js
+++ b/lib/rules/function-url-no-scheme-relative/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/function-url-quotes/__tests__/index.js b/lib/rules/function-url-quotes/__tests__/index.mjs
similarity index 98%
rename from lib/rules/function-url-quotes/__tests__/index.js
rename to lib/rules/function-url-quotes/__tests__/index.mjs
index fea07de90c..cb30725b63 100644
--- a/lib/rules/function-url-quotes/__tests__/index.js
+++ b/lib/rules/function-url-quotes/__tests__/index.mjs
@@ -1,10 +1,9 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const { stripIndent } = require('common-tags');
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/function-url-scheme-allowed-list/__tests__/index.js b/lib/rules/function-url-scheme-allowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/function-url-scheme-allowed-list/__tests__/index.js
rename to lib/rules/function-url-scheme-allowed-list/__tests__/index.mjs
index 30aa16c460..bb81cc8ddc 100644
--- a/lib/rules/function-url-scheme-allowed-list/__tests__/index.js
+++ b/lib/rules/function-url-scheme-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/function-url-scheme-disallowed-list/__tests__/index.js b/lib/rules/function-url-scheme-disallowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/function-url-scheme-disallowed-list/__tests__/index.js
rename to lib/rules/function-url-scheme-disallowed-list/__tests__/index.mjs
index c1c6bc52b5..509b7ee190 100644
--- a/lib/rules/function-url-scheme-disallowed-list/__tests__/index.js
+++ b/lib/rules/function-url-scheme-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/hue-degree-notation/__tests__/index.js b/lib/rules/hue-degree-notation/__tests__/index.mjs
similarity index 98%
rename from lib/rules/hue-degree-notation/__tests__/index.js
rename to lib/rules/hue-degree-notation/__tests__/index.mjs
index d5cfbd31ed..7fe2e44ecb 100644
--- a/lib/rules/hue-degree-notation/__tests__/index.js
+++ b/lib/rules/hue-degree-notation/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const stripIndent = require('common-tags').stripIndent;
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/import-notation/__tests__/index.js b/lib/rules/import-notation/__tests__/index.mjs
similarity index 98%
rename from lib/rules/import-notation/__tests__/index.js
rename to lib/rules/import-notation/__tests__/index.mjs
index 2e1d1cb926..52b6d5a1c1 100644
--- a/lib/rules/import-notation/__tests__/index.js
+++ b/lib/rules/import-notation/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/keyframe-block-no-duplicate-selectors/__tests__/index.js b/lib/rules/keyframe-block-no-duplicate-selectors/__tests__/index.mjs
similarity index 94%
rename from lib/rules/keyframe-block-no-duplicate-selectors/__tests__/index.js
rename to lib/rules/keyframe-block-no-duplicate-selectors/__tests__/index.mjs
index 19c7116c61..746780e0d9 100644
--- a/lib/rules/keyframe-block-no-duplicate-selectors/__tests__/index.js
+++ b/lib/rules/keyframe-block-no-duplicate-selectors/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/keyframe-declaration-no-important/__tests__/index.js b/lib/rules/keyframe-declaration-no-important/__tests__/index.mjs
similarity index 96%
rename from lib/rules/keyframe-declaration-no-important/__tests__/index.js
rename to lib/rules/keyframe-declaration-no-important/__tests__/index.mjs
index d3546646a3..f081a45595 100644
--- a/lib/rules/keyframe-declaration-no-important/__tests__/index.js
+++ b/lib/rules/keyframe-declaration-no-important/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/keyframe-selector-notation/__tests__/index.js b/lib/rules/keyframe-selector-notation/__tests__/index.mjs
similarity index 99%
rename from lib/rules/keyframe-selector-notation/__tests__/index.js
rename to lib/rules/keyframe-selector-notation/__tests__/index.mjs
index 1066dd5fbc..f5358c47f3 100644
--- a/lib/rules/keyframe-selector-notation/__tests__/index.js
+++ b/lib/rules/keyframe-selector-notation/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 const ACCEPT_TIMELINE_RANGE_NAME_TEST_CASES = [
 	{
diff --git a/lib/rules/keyframes-name-pattern/__tests__/index.js b/lib/rules/keyframes-name-pattern/__tests__/index.mjs
similarity index 95%
rename from lib/rules/keyframes-name-pattern/__tests__/index.js
rename to lib/rules/keyframes-name-pattern/__tests__/index.mjs
index 3dc964a838..6fefbcf715 100644
--- a/lib/rules/keyframes-name-pattern/__tests__/index.js
+++ b/lib/rules/keyframes-name-pattern/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/length-zero-no-unit/__tests__/index.js b/lib/rules/length-zero-no-unit/__tests__/index.mjs
similarity index 99%
rename from lib/rules/length-zero-no-unit/__tests__/index.js
rename to lib/rules/length-zero-no-unit/__tests__/index.mjs
index 9fc8a46db7..efe74e2d4b 100644
--- a/lib/rules/length-zero-no-unit/__tests__/index.js
+++ b/lib/rules/length-zero-no-unit/__tests__/index.mjs
@@ -1,7 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const { messages, ruleName } = require('..');
-const { stripIndent } = require('common-tags');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/max-nesting-depth/__tests__/index.js b/lib/rules/max-nesting-depth/__tests__/index.mjs
similarity index 97%
rename from lib/rules/max-nesting-depth/__tests__/index.js
rename to lib/rules/max-nesting-depth/__tests__/index.mjs
index 30a7629d74..44c042c2b9 100644
--- a/lib/rules/max-nesting-depth/__tests__/index.js
+++ b/lib/rules/max-nesting-depth/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const { stripIndent } = require('common-tags');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/media-feature-name-allowed-list/__tests__/index.js b/lib/rules/media-feature-name-allowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/media-feature-name-allowed-list/__tests__/index.js
rename to lib/rules/media-feature-name-allowed-list/__tests__/index.mjs
index 34e8eb98eb..16524def1c 100644
--- a/lib/rules/media-feature-name-allowed-list/__tests__/index.js
+++ b/lib/rules/media-feature-name-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/media-feature-name-disallowed-list/__tests__/index.js b/lib/rules/media-feature-name-disallowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/media-feature-name-disallowed-list/__tests__/index.js
rename to lib/rules/media-feature-name-disallowed-list/__tests__/index.mjs
index 1d30bcf7dc..71afbd9121 100644
--- a/lib/rules/media-feature-name-disallowed-list/__tests__/index.js
+++ b/lib/rules/media-feature-name-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/media-feature-name-no-unknown/__tests__/index.js b/lib/rules/media-feature-name-no-unknown/__tests__/index.mjs
similarity index 99%
rename from lib/rules/media-feature-name-no-unknown/__tests__/index.js
rename to lib/rules/media-feature-name-no-unknown/__tests__/index.mjs
index 232a90b06c..f82dfac5ed 100644
--- a/lib/rules/media-feature-name-no-unknown/__tests__/index.js
+++ b/lib/rules/media-feature-name-no-unknown/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/media-feature-name-no-vendor-prefix/__tests__/index.js b/lib/rules/media-feature-name-no-vendor-prefix/__tests__/index.mjs
similarity index 96%
rename from lib/rules/media-feature-name-no-vendor-prefix/__tests__/index.js
rename to lib/rules/media-feature-name-no-vendor-prefix/__tests__/index.mjs
index 2535ad7077..eae54d6fbb 100644
--- a/lib/rules/media-feature-name-no-vendor-prefix/__tests__/index.js
+++ b/lib/rules/media-feature-name-no-vendor-prefix/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/media-feature-name-unit-allowed-list/__tests__/index.js b/lib/rules/media-feature-name-unit-allowed-list/__tests__/index.mjs
similarity index 97%
rename from lib/rules/media-feature-name-unit-allowed-list/__tests__/index.js
rename to lib/rules/media-feature-name-unit-allowed-list/__tests__/index.mjs
index 813026e3de..45c505f505 100644
--- a/lib/rules/media-feature-name-unit-allowed-list/__tests__/index.js
+++ b/lib/rules/media-feature-name-unit-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/media-feature-name-value-allowed-list/__tests__/index.js b/lib/rules/media-feature-name-value-allowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/media-feature-name-value-allowed-list/__tests__/index.js
rename to lib/rules/media-feature-name-value-allowed-list/__tests__/index.mjs
index 65faa7b111..1448caf30b 100644
--- a/lib/rules/media-feature-name-value-allowed-list/__tests__/index.js
+++ b/lib/rules/media-feature-name-value-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/media-feature-name-value-no-unknown/__tests__/index.js b/lib/rules/media-feature-name-value-no-unknown/__tests__/index.mjs
similarity index 99%
rename from lib/rules/media-feature-name-value-no-unknown/__tests__/index.js
rename to lib/rules/media-feature-name-value-no-unknown/__tests__/index.mjs
index e68848e4e5..7e25ca5b57 100644
--- a/lib/rules/media-feature-name-value-no-unknown/__tests__/index.js
+++ b/lib/rules/media-feature-name-value-no-unknown/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/media-feature-range-notation/__tests__/index.js b/lib/rules/media-feature-range-notation/__tests__/index.mjs
similarity index 97%
rename from lib/rules/media-feature-range-notation/__tests__/index.js
rename to lib/rules/media-feature-range-notation/__tests__/index.mjs
index 8416abef19..d81ac62505 100644
--- a/lib/rules/media-feature-range-notation/__tests__/index.js
+++ b/lib/rules/media-feature-range-notation/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const { stripIndent } = require('common-tags');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/media-query-no-invalid/__tests__/index.js b/lib/rules/media-query-no-invalid/__tests__/index.mjs
similarity index 98%
rename from lib/rules/media-query-no-invalid/__tests__/index.js
rename to lib/rules/media-query-no-invalid/__tests__/index.mjs
index 1582375c40..6e72ed00d9 100644
--- a/lib/rules/media-query-no-invalid/__tests__/index.js
+++ b/lib/rules/media-query-no-invalid/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/named-grid-areas-no-invalid/__tests__/index.js b/lib/rules/named-grid-areas-no-invalid/__tests__/index.mjs
similarity index 97%
rename from lib/rules/named-grid-areas-no-invalid/__tests__/index.js
rename to lib/rules/named-grid-areas-no-invalid/__tests__/index.mjs
index dfd4552ab6..7b448c8ed5 100644
--- a/lib/rules/named-grid-areas-no-invalid/__tests__/index.js
+++ b/lib/rules/named-grid-areas-no-invalid/__tests__/index.mjs
@@ -1,7 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const { stripIndent } = require('common-tags');
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/no-descending-specificity/__tests__/index.js b/lib/rules/no-descending-specificity/__tests__/index.mjs
similarity index 95%
rename from lib/rules/no-descending-specificity/__tests__/index.js
rename to lib/rules/no-descending-specificity/__tests__/index.mjs
index dd02f2877c..224d417037 100644
--- a/lib/rules/no-descending-specificity/__tests__/index.js
+++ b/lib/rules/no-descending-specificity/__tests__/index.mjs
@@ -1,10 +1,9 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const { stripIndent } = require('common-tags');
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/no-duplicate-at-import-rules/__tests__/index.js b/lib/rules/no-duplicate-at-import-rules/__tests__/index.mjs
similarity index 98%
rename from lib/rules/no-duplicate-at-import-rules/__tests__/index.js
rename to lib/rules/no-duplicate-at-import-rules/__tests__/index.mjs
index b09d3cd17e..037438d7c5 100644
--- a/lib/rules/no-duplicate-at-import-rules/__tests__/index.js
+++ b/lib/rules/no-duplicate-at-import-rules/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/no-duplicate-selectors/__tests__/index.js b/lib/rules/no-duplicate-selectors/__tests__/index.mjs
similarity index 94%
rename from lib/rules/no-duplicate-selectors/__tests__/index.js
rename to lib/rules/no-duplicate-selectors/__tests__/index.mjs
index a3cd86cbcb..4bccc60b1a 100644
--- a/lib/rules/no-duplicate-selectors/__tests__/index.js
+++ b/lib/rules/no-duplicate-selectors/__tests__/index.mjs
@@ -1,13 +1,11 @@
-'use strict';
+import { fileURLToPath } from 'node:url';
 
-const path = require('path');
-const postcss = require('postcss');
-const postcssImport = require('postcss-import');
+import postcss from 'postcss';
+import postcssImport from 'postcss-import';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const rule = require('..');
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
+import rule from '../index.js';
 const { messages, ruleName } = rule;
 
 testRule({
@@ -264,7 +262,7 @@ testRule({
 it('with postcss-import and duplicates within a file, a warning strikes', () => {
 	return postcss([postcssImport(), rule()])
 		.process("@import 'fixtures/using-foo-twice.css';", {
-			from: path.join(__dirname, 'test.css'),
+			from: fileURLToPath(new URL('./test.css', import.meta.url)),
 		})
 		.then((result) => {
 			expect(result.warnings()).toHaveLength(1);
@@ -274,7 +272,7 @@ it('with postcss-import and duplicates within a file, a warning strikes', () =>
 it('with postcss-import and duplicates across files, no warnings', () => {
 	return postcss([postcssImport(), rule()])
 		.process("@import 'fixtures/using-foo.css'; @import 'fixtures/also-using-foo.css';", {
-			from: path.join(__dirname, 'test.css'),
+			from: fileURLToPath(new URL('./test.css', import.meta.url)),
 		})
 		.then((result) => {
 			expect(result.warnings()).toHaveLength(0);
diff --git a/lib/rules/no-empty-source/__tests__/index.js b/lib/rules/no-empty-source/__tests__/index.mjs
similarity index 96%
rename from lib/rules/no-empty-source/__tests__/index.js
rename to lib/rules/no-empty-source/__tests__/index.mjs
index b008fa96c4..461361ba93 100644
--- a/lib/rules/no-empty-source/__tests__/index.js
+++ b/lib/rules/no-empty-source/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/no-invalid-double-slash-comments/__tests__/index.js b/lib/rules/no-invalid-double-slash-comments/__tests__/index.mjs
similarity index 96%
rename from lib/rules/no-invalid-double-slash-comments/__tests__/index.js
rename to lib/rules/no-invalid-double-slash-comments/__tests__/index.mjs
index 2b7ccede99..9dbe0dbdb1 100644
--- a/lib/rules/no-invalid-double-slash-comments/__tests__/index.js
+++ b/lib/rules/no-invalid-double-slash-comments/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/no-invalid-position-at-import-rule/__tests__/index.js b/lib/rules/no-invalid-position-at-import-rule/__tests__/index.mjs
similarity index 96%
rename from lib/rules/no-invalid-position-at-import-rule/__tests__/index.js
rename to lib/rules/no-invalid-position-at-import-rule/__tests__/index.mjs
index c33091f004..ca73f1dbe7 100644
--- a/lib/rules/no-invalid-position-at-import-rule/__tests__/index.js
+++ b/lib/rules/no-invalid-position-at-import-rule/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const stripIndent = require('common-tags').stripIndent;
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/no-irregular-whitespace/__tests__/index.js b/lib/rules/no-irregular-whitespace/__tests__/index.mjs
similarity index 97%
rename from lib/rules/no-irregular-whitespace/__tests__/index.js
rename to lib/rules/no-irregular-whitespace/__tests__/index.mjs
index 0cedde66de..6e773f106a 100644
--- a/lib/rules/no-irregular-whitespace/__tests__/index.js
+++ b/lib/rules/no-irregular-whitespace/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 const IRREGULAR_WHITESPACES = [
 	'\u000B', // Line Tabulation (\v) - <VT>
diff --git a/lib/rules/no-unknown-animations/__tests__/index.js b/lib/rules/no-unknown-animations/__tests__/index.mjs
similarity index 98%
rename from lib/rules/no-unknown-animations/__tests__/index.js
rename to lib/rules/no-unknown-animations/__tests__/index.mjs
index 2f053e77af..6f8c40766d 100644
--- a/lib/rules/no-unknown-animations/__tests__/index.js
+++ b/lib/rules/no-unknown-animations/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/no-unknown-custom-properties/__tests__/index.js b/lib/rules/no-unknown-custom-properties/__tests__/index.mjs
similarity index 93%
rename from lib/rules/no-unknown-custom-properties/__tests__/index.js
rename to lib/rules/no-unknown-custom-properties/__tests__/index.mjs
index 9e0e2bd7c5..208384b143 100644
--- a/lib/rules/no-unknown-custom-properties/__tests__/index.js
+++ b/lib/rules/no-unknown-custom-properties/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const { stripIndent } = require('common-tags');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/number-max-precision/__tests__/index.js b/lib/rules/number-max-precision/__tests__/index.mjs
similarity index 98%
rename from lib/rules/number-max-precision/__tests__/index.js
rename to lib/rules/number-max-precision/__tests__/index.mjs
index eab6754b40..d398018053 100644
--- a/lib/rules/number-max-precision/__tests__/index.js
+++ b/lib/rules/number-max-precision/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/property-allowed-list/__tests__/index.js b/lib/rules/property-allowed-list/__tests__/index.mjs
similarity index 97%
rename from lib/rules/property-allowed-list/__tests__/index.js
rename to lib/rules/property-allowed-list/__tests__/index.mjs
index d4c680c2e0..cb0ed90a02 100644
--- a/lib/rules/property-allowed-list/__tests__/index.js
+++ b/lib/rules/property-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/property-disallowed-list/__tests__/index.js b/lib/rules/property-disallowed-list/__tests__/index.mjs
similarity index 97%
rename from lib/rules/property-disallowed-list/__tests__/index.js
rename to lib/rules/property-disallowed-list/__tests__/index.mjs
index d14e5c1387..d375d95f5f 100644
--- a/lib/rules/property-disallowed-list/__tests__/index.js
+++ b/lib/rules/property-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/property-no-unknown/__tests__/index.js b/lib/rules/property-no-unknown/__tests__/index.mjs
similarity index 97%
rename from lib/rules/property-no-unknown/__tests__/index.js
rename to lib/rules/property-no-unknown/__tests__/index.mjs
index 9177da9083..3ef72ac521 100644
--- a/lib/rules/property-no-unknown/__tests__/index.js
+++ b/lib/rules/property-no-unknown/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/property-no-vendor-prefix/__tests__/index.js b/lib/rules/property-no-vendor-prefix/__tests__/index.mjs
similarity index 98%
rename from lib/rules/property-no-vendor-prefix/__tests__/index.js
rename to lib/rules/property-no-vendor-prefix/__tests__/index.mjs
index 4611f0b14a..1bd6301d79 100644
--- a/lib/rules/property-no-vendor-prefix/__tests__/index.js
+++ b/lib/rules/property-no-vendor-prefix/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/rule-empty-line-before/__tests__/index.js b/lib/rules/rule-empty-line-before/__tests__/index.mjs
similarity index 99%
rename from lib/rules/rule-empty-line-before/__tests__/index.js
rename to lib/rules/rule-empty-line-before/__tests__/index.mjs
index 3b47808c59..4ccd56d7fa 100644
--- a/lib/rules/rule-empty-line-before/__tests__/index.js
+++ b/lib/rules/rule-empty-line-before/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/rule-selector-property-disallowed-list/__tests__/index.js b/lib/rules/rule-selector-property-disallowed-list/__tests__/index.mjs
similarity index 96%
rename from lib/rules/rule-selector-property-disallowed-list/__tests__/index.js
rename to lib/rules/rule-selector-property-disallowed-list/__tests__/index.mjs
index 8baa936a30..cf65ea4bf5 100644
--- a/lib/rules/rule-selector-property-disallowed-list/__tests__/index.js
+++ b/lib/rules/rule-selector-property-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-anb-no-unmatchable/__tests__/index.js b/lib/rules/selector-anb-no-unmatchable/__tests__/index.mjs
similarity index 97%
rename from lib/rules/selector-anb-no-unmatchable/__tests__/index.js
rename to lib/rules/selector-anb-no-unmatchable/__tests__/index.mjs
index 21d9d9d432..85c1cc33b6 100644
--- a/lib/rules/selector-anb-no-unmatchable/__tests__/index.js
+++ b/lib/rules/selector-anb-no-unmatchable/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-attribute-name-disallowed-list/__tests__/index.js b/lib/rules/selector-attribute-name-disallowed-list/__tests__/index.mjs
similarity index 95%
rename from lib/rules/selector-attribute-name-disallowed-list/__tests__/index.js
rename to lib/rules/selector-attribute-name-disallowed-list/__tests__/index.mjs
index 9d76879709..cb3acf24a7 100644
--- a/lib/rules/selector-attribute-name-disallowed-list/__tests__/index.js
+++ b/lib/rules/selector-attribute-name-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-attribute-operator-allowed-list/__tests__/index.js b/lib/rules/selector-attribute-operator-allowed-list/__tests__/index.mjs
similarity index 95%
rename from lib/rules/selector-attribute-operator-allowed-list/__tests__/index.js
rename to lib/rules/selector-attribute-operator-allowed-list/__tests__/index.mjs
index 76af7c1fc6..f7aa15b05c 100644
--- a/lib/rules/selector-attribute-operator-allowed-list/__tests__/index.js
+++ b/lib/rules/selector-attribute-operator-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-attribute-operator-disallowed-list/__tests__/index.js b/lib/rules/selector-attribute-operator-disallowed-list/__tests__/index.mjs
similarity index 95%
rename from lib/rules/selector-attribute-operator-disallowed-list/__tests__/index.js
rename to lib/rules/selector-attribute-operator-disallowed-list/__tests__/index.mjs
index f292fe991a..19ee99cbc3 100644
--- a/lib/rules/selector-attribute-operator-disallowed-list/__tests__/index.js
+++ b/lib/rules/selector-attribute-operator-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-attribute-quotes/__tests__/index.js b/lib/rules/selector-attribute-quotes/__tests__/index.mjs
similarity index 99%
rename from lib/rules/selector-attribute-quotes/__tests__/index.js
rename to lib/rules/selector-attribute-quotes/__tests__/index.mjs
index a0ac91fb55..34a2fee164 100644
--- a/lib/rules/selector-attribute-quotes/__tests__/index.js
+++ b/lib/rules/selector-attribute-quotes/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-class-pattern/__tests__/index.js b/lib/rules/selector-class-pattern/__tests__/index.mjs
similarity index 98%
rename from lib/rules/selector-class-pattern/__tests__/index.js
rename to lib/rules/selector-class-pattern/__tests__/index.mjs
index ba40f23fd3..4941f1f913 100644
--- a/lib/rules/selector-class-pattern/__tests__/index.js
+++ b/lib/rules/selector-class-pattern/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 const basicAZTestsAccept = {
 	accept: [
diff --git a/lib/rules/selector-combinator-allowed-list/__tests__/index.js b/lib/rules/selector-combinator-allowed-list/__tests__/index.mjs
similarity index 94%
rename from lib/rules/selector-combinator-allowed-list/__tests__/index.js
rename to lib/rules/selector-combinator-allowed-list/__tests__/index.mjs
index 4b28f7ed5d..d61b30bef9 100644
--- a/lib/rules/selector-combinator-allowed-list/__tests__/index.js
+++ b/lib/rules/selector-combinator-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-combinator-disallowed-list/__tests__/index.js b/lib/rules/selector-combinator-disallowed-list/__tests__/index.mjs
similarity index 94%
rename from lib/rules/selector-combinator-disallowed-list/__tests__/index.js
rename to lib/rules/selector-combinator-disallowed-list/__tests__/index.mjs
index ad5a8c6b69..0026c5b437 100644
--- a/lib/rules/selector-combinator-disallowed-list/__tests__/index.js
+++ b/lib/rules/selector-combinator-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-disallowed-list/__tests__/index.js b/lib/rules/selector-disallowed-list/__tests__/index.mjs
similarity index 97%
rename from lib/rules/selector-disallowed-list/__tests__/index.js
rename to lib/rules/selector-disallowed-list/__tests__/index.mjs
index 3668436749..71b355abc2 100644
--- a/lib/rules/selector-disallowed-list/__tests__/index.js
+++ b/lib/rules/selector-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-id-pattern/__tests__/index.js b/lib/rules/selector-id-pattern/__tests__/index.mjs
similarity index 96%
rename from lib/rules/selector-id-pattern/__tests__/index.js
rename to lib/rules/selector-id-pattern/__tests__/index.mjs
index fdd626db05..2f53dd3c43 100644
--- a/lib/rules/selector-id-pattern/__tests__/index.js
+++ b/lib/rules/selector-id-pattern/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 const basicAZTests = {
 	accept: [
diff --git a/lib/rules/selector-max-attribute/__tests__/index.js b/lib/rules/selector-max-attribute/__tests__/index.mjs
similarity index 99%
rename from lib/rules/selector-max-attribute/__tests__/index.js
rename to lib/rules/selector-max-attribute/__tests__/index.mjs
index 2ed7fd16cf..ecbc6051dd 100644
--- a/lib/rules/selector-max-attribute/__tests__/index.js
+++ b/lib/rules/selector-max-attribute/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 // Sanity checks
 testRule({
diff --git a/lib/rules/selector-max-class/__tests__/index.js b/lib/rules/selector-max-class/__tests__/index.mjs
similarity index 98%
rename from lib/rules/selector-max-class/__tests__/index.js
rename to lib/rules/selector-max-class/__tests__/index.mjs
index 99ce71a322..59ed0fa8ea 100644
--- a/lib/rules/selector-max-class/__tests__/index.js
+++ b/lib/rules/selector-max-class/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 // Sanity checks
 testRule({
diff --git a/lib/rules/selector-max-combinators/__tests__/index.js b/lib/rules/selector-max-combinators/__tests__/index.mjs
similarity index 99%
rename from lib/rules/selector-max-combinators/__tests__/index.js
rename to lib/rules/selector-max-combinators/__tests__/index.mjs
index da827298cd..c72f638d85 100644
--- a/lib/rules/selector-max-combinators/__tests__/index.js
+++ b/lib/rules/selector-max-combinators/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 // Sanity checks
 testRule({
diff --git a/lib/rules/selector-max-compound-selectors/__tests__/index.js b/lib/rules/selector-max-compound-selectors/__tests__/index.mjs
similarity index 99%
rename from lib/rules/selector-max-compound-selectors/__tests__/index.js
rename to lib/rules/selector-max-compound-selectors/__tests__/index.mjs
index a50bfb3022..a79a423eaf 100644
--- a/lib/rules/selector-max-compound-selectors/__tests__/index.js
+++ b/lib/rules/selector-max-compound-selectors/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 // Testing plain selectors, different combinators
 testRule({
diff --git a/lib/rules/selector-max-id/__tests__/index.js b/lib/rules/selector-max-id/__tests__/index.mjs
similarity index 99%
rename from lib/rules/selector-max-id/__tests__/index.js
rename to lib/rules/selector-max-id/__tests__/index.mjs
index c574945dfc..b200cafea0 100644
--- a/lib/rules/selector-max-id/__tests__/index.js
+++ b/lib/rules/selector-max-id/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 // Sanity checks
 testRule({
diff --git a/lib/rules/selector-max-pseudo-class/__tests__/index.js b/lib/rules/selector-max-pseudo-class/__tests__/index.mjs
similarity index 98%
rename from lib/rules/selector-max-pseudo-class/__tests__/index.js
rename to lib/rules/selector-max-pseudo-class/__tests__/index.mjs
index d994bb4890..c52dcf2ae1 100644
--- a/lib/rules/selector-max-pseudo-class/__tests__/index.js
+++ b/lib/rules/selector-max-pseudo-class/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-max-specificity/__tests__/index.js b/lib/rules/selector-max-specificity/__tests__/index.mjs
similarity index 99%
rename from lib/rules/selector-max-specificity/__tests__/index.js
rename to lib/rules/selector-max-specificity/__tests__/index.mjs
index 70022e119e..2e31be7d6e 100644
--- a/lib/rules/selector-max-specificity/__tests__/index.js
+++ b/lib/rules/selector-max-specificity/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-max-type/__tests__/index.js b/lib/rules/selector-max-type/__tests__/index.mjs
similarity index 99%
rename from lib/rules/selector-max-type/__tests__/index.js
rename to lib/rules/selector-max-type/__tests__/index.mjs
index 6d13b85ca4..46c656786b 100644
--- a/lib/rules/selector-max-type/__tests__/index.js
+++ b/lib/rules/selector-max-type/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 // Sanity checks
 testRule({
diff --git a/lib/rules/selector-max-universal/__tests__/index.js b/lib/rules/selector-max-universal/__tests__/index.mjs
similarity index 99%
rename from lib/rules/selector-max-universal/__tests__/index.js
rename to lib/rules/selector-max-universal/__tests__/index.mjs
index fd35306c1f..dfec24afc5 100644
--- a/lib/rules/selector-max-universal/__tests__/index.js
+++ b/lib/rules/selector-max-universal/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 // Sanity checks
 testRule({
diff --git a/lib/rules/selector-nested-pattern/__tests__/index.js b/lib/rules/selector-nested-pattern/__tests__/index.mjs
similarity index 96%
rename from lib/rules/selector-nested-pattern/__tests__/index.js
rename to lib/rules/selector-nested-pattern/__tests__/index.mjs
index e9288f5674..f074bfe17c 100644
--- a/lib/rules/selector-nested-pattern/__tests__/index.js
+++ b/lib/rules/selector-nested-pattern/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const stripIndent = require('common-tags').stripIndent;
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 const basicAZTests = {
 	accept: [
diff --git a/lib/rules/selector-no-qualifying-type/__tests__/index.js b/lib/rules/selector-no-qualifying-type/__tests__/index.mjs
similarity index 99%
rename from lib/rules/selector-no-qualifying-type/__tests__/index.js
rename to lib/rules/selector-no-qualifying-type/__tests__/index.mjs
index 8be5893e8d..423a04521f 100644
--- a/lib/rules/selector-no-qualifying-type/__tests__/index.js
+++ b/lib/rules/selector-no-qualifying-type/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const { stripIndent } = require('common-tags');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-no-vendor-prefix/__tests__/index.js b/lib/rules/selector-no-vendor-prefix/__tests__/index.mjs
similarity index 97%
rename from lib/rules/selector-no-vendor-prefix/__tests__/index.js
rename to lib/rules/selector-no-vendor-prefix/__tests__/index.mjs
index 4b776079bd..97c48c125b 100644
--- a/lib/rules/selector-no-vendor-prefix/__tests__/index.js
+++ b/lib/rules/selector-no-vendor-prefix/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-not-notation/__tests__/index.js b/lib/rules/selector-not-notation/__tests__/index.mjs
similarity index 97%
rename from lib/rules/selector-not-notation/__tests__/index.js
rename to lib/rules/selector-not-notation/__tests__/index.mjs
index d77d371a5b..5bb30f92b0 100644
--- a/lib/rules/selector-not-notation/__tests__/index.js
+++ b/lib/rules/selector-not-notation/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-pseudo-class-allowed-list/__tests__/index.js b/lib/rules/selector-pseudo-class-allowed-list/__tests__/index.mjs
similarity index 97%
rename from lib/rules/selector-pseudo-class-allowed-list/__tests__/index.js
rename to lib/rules/selector-pseudo-class-allowed-list/__tests__/index.mjs
index c65be9a5fa..76aa9b024b 100644
--- a/lib/rules/selector-pseudo-class-allowed-list/__tests__/index.js
+++ b/lib/rules/selector-pseudo-class-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-pseudo-class-disallowed-list/__tests__/index.js b/lib/rules/selector-pseudo-class-disallowed-list/__tests__/index.mjs
similarity index 98%
rename from lib/rules/selector-pseudo-class-disallowed-list/__tests__/index.js
rename to lib/rules/selector-pseudo-class-disallowed-list/__tests__/index.mjs
index 781aa83ad6..21ccb6db2c 100644
--- a/lib/rules/selector-pseudo-class-disallowed-list/__tests__/index.js
+++ b/lib/rules/selector-pseudo-class-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-pseudo-class-no-unknown/__tests__/index.js b/lib/rules/selector-pseudo-class-no-unknown/__tests__/index.mjs
similarity index 98%
rename from lib/rules/selector-pseudo-class-no-unknown/__tests__/index.js
rename to lib/rules/selector-pseudo-class-no-unknown/__tests__/index.mjs
index 31e9b4def1..960a6282e8 100644
--- a/lib/rules/selector-pseudo-class-no-unknown/__tests__/index.js
+++ b/lib/rules/selector-pseudo-class-no-unknown/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-pseudo-element-allowed-list/__tests__/index.js b/lib/rules/selector-pseudo-element-allowed-list/__tests__/index.mjs
similarity index 96%
rename from lib/rules/selector-pseudo-element-allowed-list/__tests__/index.js
rename to lib/rules/selector-pseudo-element-allowed-list/__tests__/index.mjs
index 54bd92e902..1bdeec7e46 100644
--- a/lib/rules/selector-pseudo-element-allowed-list/__tests__/index.js
+++ b/lib/rules/selector-pseudo-element-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-pseudo-element-colon-notation/__tests__/index.js b/lib/rules/selector-pseudo-element-colon-notation/__tests__/index.mjs
similarity index 98%
rename from lib/rules/selector-pseudo-element-colon-notation/__tests__/index.js
rename to lib/rules/selector-pseudo-element-colon-notation/__tests__/index.mjs
index 465cfa06ca..915e6816ec 100644
--- a/lib/rules/selector-pseudo-element-colon-notation/__tests__/index.js
+++ b/lib/rules/selector-pseudo-element-colon-notation/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-pseudo-element-disallowed-list/__tests__/index.js b/lib/rules/selector-pseudo-element-disallowed-list/__tests__/index.mjs
similarity index 96%
rename from lib/rules/selector-pseudo-element-disallowed-list/__tests__/index.js
rename to lib/rules/selector-pseudo-element-disallowed-list/__tests__/index.mjs
index 57fb817b2e..aa64ffa485 100644
--- a/lib/rules/selector-pseudo-element-disallowed-list/__tests__/index.js
+++ b/lib/rules/selector-pseudo-element-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-pseudo-element-no-unknown/__tests__/index.js b/lib/rules/selector-pseudo-element-no-unknown/__tests__/index.mjs
similarity index 98%
rename from lib/rules/selector-pseudo-element-no-unknown/__tests__/index.js
rename to lib/rules/selector-pseudo-element-no-unknown/__tests__/index.mjs
index d9e2f23f6d..cfad30b607 100644
--- a/lib/rules/selector-pseudo-element-no-unknown/__tests__/index.js
+++ b/lib/rules/selector-pseudo-element-no-unknown/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-type-case/__tests__/index.js b/lib/rules/selector-type-case/__tests__/index.mjs
similarity index 98%
rename from lib/rules/selector-type-case/__tests__/index.js
rename to lib/rules/selector-type-case/__tests__/index.mjs
index 3fcbbf4186..c7bbdbe120 100644
--- a/lib/rules/selector-type-case/__tests__/index.js
+++ b/lib/rules/selector-type-case/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/selector-type-no-unknown/__tests__/index.js b/lib/rules/selector-type-no-unknown/__tests__/index.mjs
similarity index 97%
rename from lib/rules/selector-type-no-unknown/__tests__/index.js
rename to lib/rules/selector-type-no-unknown/__tests__/index.mjs
index 9dba9c7d07..e49655e0e7 100644
--- a/lib/rules/selector-type-no-unknown/__tests__/index.js
+++ b/lib/rules/selector-type-no-unknown/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import naiveCssInJs from '../../../__tests__/fixtures/postcss-naive-css-in-js.js';
 
-const naiveCssInJs = require('../../../__tests__/fixtures/postcss-naive-css-in-js');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/shorthand-property-no-redundant-values/__tests__/index.js b/lib/rules/shorthand-property-no-redundant-values/__tests__/index.mjs
similarity index 99%
rename from lib/rules/shorthand-property-no-redundant-values/__tests__/index.js
rename to lib/rules/shorthand-property-no-redundant-values/__tests__/index.mjs
index 33eabced6e..08cb20baf0 100644
--- a/lib/rules/shorthand-property-no-redundant-values/__tests__/index.js
+++ b/lib/rules/shorthand-property-no-redundant-values/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/string-no-newline/__tests__/index.js b/lib/rules/string-no-newline/__tests__/index.mjs
similarity index 95%
rename from lib/rules/string-no-newline/__tests__/index.js
rename to lib/rules/string-no-newline/__tests__/index.mjs
index 2b05f376e9..a8a112c343 100644
--- a/lib/rules/string-no-newline/__tests__/index.js
+++ b/lib/rules/string-no-newline/__tests__/index.mjs
@@ -1,8 +1,7 @@
-'use strict';
+import { stripIndent } from 'common-tags';
 
-const { stripIndent } = require('common-tags');
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/time-min-milliseconds/__tests__/index.js b/lib/rules/time-min-milliseconds/__tests__/index.mjs
similarity index 99%
rename from lib/rules/time-min-milliseconds/__tests__/index.js
rename to lib/rules/time-min-milliseconds/__tests__/index.mjs
index 24249c220f..2fd0d0ddd0 100644
--- a/lib/rules/time-min-milliseconds/__tests__/index.js
+++ b/lib/rules/time-min-milliseconds/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 const MIN_VALUE = 100;
 
diff --git a/lib/rules/unit-allowed-list/__tests__/index.js b/lib/rules/unit-allowed-list/__tests__/index.mjs
similarity index 99%
rename from lib/rules/unit-allowed-list/__tests__/index.js
rename to lib/rules/unit-allowed-list/__tests__/index.mjs
index e1a92243bb..30c8a1ebe9 100644
--- a/lib/rules/unit-allowed-list/__tests__/index.js
+++ b/lib/rules/unit-allowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/unit-disallowed-list/__tests__/index.js b/lib/rules/unit-disallowed-list/__tests__/index.mjs
similarity index 99%
rename from lib/rules/unit-disallowed-list/__tests__/index.js
rename to lib/rules/unit-disallowed-list/__tests__/index.mjs
index ad135ca3cb..8d5765d117 100644
--- a/lib/rules/unit-disallowed-list/__tests__/index.js
+++ b/lib/rules/unit-disallowed-list/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/unit-no-unknown/__tests__/index.js b/lib/rules/unit-no-unknown/__tests__/index.mjs
similarity index 99%
rename from lib/rules/unit-no-unknown/__tests__/index.js
rename to lib/rules/unit-no-unknown/__tests__/index.mjs
index b98e0c6b27..b4dc2601aa 100644
--- a/lib/rules/unit-no-unknown/__tests__/index.js
+++ b/lib/rules/unit-no-unknown/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/value-keyword-case/__tests__/index.js b/lib/rules/value-keyword-case/__tests__/index.mjs
similarity index 99%
rename from lib/rules/value-keyword-case/__tests__/index.js
rename to lib/rules/value-keyword-case/__tests__/index.mjs
index 836d1a6036..b524834377 100644
--- a/lib/rules/value-keyword-case/__tests__/index.js
+++ b/lib/rules/value-keyword-case/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,
diff --git a/lib/rules/value-no-vendor-prefix/__tests__/index.js b/lib/rules/value-no-vendor-prefix/__tests__/index.mjs
similarity index 98%
rename from lib/rules/value-no-vendor-prefix/__tests__/index.js
rename to lib/rules/value-no-vendor-prefix/__tests__/index.mjs
index 1eced4af18..870093d4a0 100644
--- a/lib/rules/value-no-vendor-prefix/__tests__/index.js
+++ b/lib/rules/value-no-vendor-prefix/__tests__/index.mjs
@@ -1,6 +1,5 @@
-'use strict';
-
-const { messages, ruleName } = require('..');
+import rule from '../index.js';
+const { messages, ruleName } = rule;
 
 testRule({
 	ruleName,