Add toPassAxeTests feature (#494)

.changeset/early-pigs-beg.md

@@ -0,0 +1,22 @@
+---
+'pleasantest': minor
+---
+
+New assertion: `expect(page).toPassAxeTests()`
+
+This assertion is based on the [`jest-puppeteer-axe`](https://github.com/WordPress/gutenberg/tree/3b2eccc289cfc90bd99252b12fc4c6e470ce4c04/packages/jest-puppeteer-axe) package. (That package already works with Pleasantest, our new feature just formats error messages a little differently)
+
+It allows you to pass a page to be checked with the [axe accessibility linter](https://github.com/dequelabs/axe-core).
+
+```js
+test(
+  'Axe tests',
+  withBrowser(async ({ utils, page }) => {
+    await utils.injectHTML(`
+      <h1>Some html</h1>
+    `);
+
+    await expect(page).toPassAxeTests();
+  }),
+);
+```

README.md

@@ -35,6 +35,7 @@ Pleasantest is a library that allows you test web applications using real browse
   - [Utilities API: `PleasantestUtils`](#utilities-api-pleasantestutils)
   - [`jest-dom` Matchers](#jest-dom-matchers)
   - [`getAccessibilityTree`](#getaccessibilitytreeelement-elementhandle--page-options-accessibilitytreeoptions--promiseaccessibilitytreesnapshot)
+  - [`toPassAxeTests`](#expectpagetopassaxetestsopts-topassaxetestsopts)
 - [Puppeteer Tips](#puppeteer-tips)
 - [Comparisons with other testing tools](#comparisons-with-other-testing-tools)
 - [Limitations](#limitationsarchitectural-decisions)
@@ -830,6 +831,33 @@ Disabling these options can be used to reduce the output or to exclude text that
 
 The returned `Promise` wraps an `AccessibilityTreeSnapshot`, which can be passed directly as the `expect` first parameter in `expect(___).toMatchInlineSnapshot()`. The returned object can also be converted to a string using `String(accessibilityTreeSnapshot)`.
 
+### `expect(page).toPassAxeTests(opts?: ToPassAxeTestsOpts)`
+
+This assertion, based on [`jest-puppeteer-axe`](https://github.com/WordPress/gutenberg/tree/3b2eccc289cfc90bd99252b12fc4c6e470ce4c04/packages/jest-puppeteer-axe), allows you to check a page using the [axe accessibility linter](https://github.com/dequelabs/axe-core).
+
+To use this assertion, you **must install `@axe-core/puppeteer` and `axe-core`**. They are optional peer dependencies for Pleasantest, but are needed for the `toPassAxeTests` assertion.
+
+```js
+test(
+  'Axe tests',
+  withBrowser(async ({ utils, page }) => {
+    await utils.injectHTML(`
+      <h1>Some html</h1>
+    `);
+
+    await expect(page).toPassAxeTests();
+  }),
+);
+```
+
+`ToPassAxeTestsOpts` (all properties are optional):
+
+- `include`: `string | string[]`: CSS selector(s) to add to the list of elements to include in analysis.
+- `exclude`: `string | string[]`: CSS selector(s) to add to the list of elements to exclude from analysis.
+- `disabledRules`: `string | string[]`: The list of [Axe rules](https://github.com/dequelabs/axe-core/tree/v4.4.2/lib/rules) to skip from verification.
+- `options`: [`axe.RunOptions`](https://github.com/dequelabs/axe-core/blob/v4.4.2/axe.d.ts#L89): A flexible way to [configure how Axe run operates](https://github.com/dequelabs/axe-core/blob/HEAD/doc/API.md#options-parameter).
+- `config`: [`axe.Spec`](https://github.com/dequelabs/axe-core/blob/v4.4.2/axe.d.ts#L195): [Axe configuration object](https://github.com/dequelabs/axe-core/blob/HEAD/doc/API.md#api-name-axeconfigure).
+
 ## Puppeteer Tips
 
 Pleasantest uses [Puppeteer](https://github.com/puppeteer/puppeteer) under the hood. You don't need to know how to use Puppeteer in order to use Pleasantest, but a little bit of Puppeteer knowledge might come in handy. Here are the parts of Puppeteer that are most helpful and relevant for Pleasantest:

package.json

@@ -8,8 +8,21 @@
     "dist"
   ],
   "license": "MIT",
+  "peerDependencies": {
+    "@axe-core/puppeteer": "^4.4.2",
+    "axe-core": "^4.4.2"
+  },
+  "peerDependenciesMeta": {
+    "@axe-core/puppeteer": {
+      "optional": true
+    },
+    "axe-core": {
+      "optional": true
+    }
+  },
   "devDependencies": {
     "@ampproject/remapping": "2.2.0",
+    "@axe-core/puppeteer": "4.4.2",
     "@babel/core": "7.16.7",
     "@babel/preset-env": "7.16.8",
     "@babel/preset-typescript": "7.16.7",
@@ -28,6 +41,7 @@
     "@vue/compiler-sfc": "3.2.36",
     "ansi-regex": "6.0.1",
     "aria-query": "*",
+    "axe-core": "4.4.2",
     "babel-plugin-un-cjs": "2.5.0",
     "dom-accessibility-api": "0.5.14",
     "errorstacks": "2.4.0",

rollup.config.js

@@ -19,6 +19,7 @@ const external = [
   'esbuild',
   /postcss/,
   /mime/,
+  '@axe-core/puppeteer',
 ];
 
 /** @type {import('rollup').RollupOptions} */
@@ -55,7 +56,7 @@ const mainConfig = {
 const typesConfig = {
   input: 'src/index.ts',
   output: [{ file: 'dist/index.d.ts', format: 'es' }],
-  external: [...external, 'polka'],
+  external: [...external, 'polka', 'axe-core'],
   plugins: [dts({ respectExternal: true })],
 };
 

src/accessibility/browser.ts

@@ -6,6 +6,16 @@ import {
 // @ts-expect-error This is a fake file that triggers a rollup plugin
 import requiredOwnedElementsMap from 'generated:requiredOwnedElements';
 import type { AccessibilityTreeOptions } from '.';
+import * as colors from 'kolorist';
+
+export * as colors from 'kolorist';
+export { printElement } from '../serialize';
+
+// We haver to tell kolorist to print the colors
+// because by default it won't since we are in the browser
+// (the colored message gets sent to node to be printed)
+colors.options.enabled = true;
+colors.options.supportLevel = 1;
 
 const indent = (text: string, indenter = '  ') =>
   indenter + text.split('\n').join(`\n${indenter}`);