CI: Overhaul for speed 🚀 (#27180)

* Use a parallel CI workflow

* Restructure CI config with references

* Inline CircleCI test runners

* Report eslint results

* Use js for jest config

* Persist Jest caches between builds

* Better git caching

* Cache node_modules

* Reenable tests and further split

* Run integration nightly

* Remove CI splitting for non-parallel jobs

* Test results by directory not filename

* Try timings again with cache-bust

* Add 2m timeout to Jest

I've observed a hung test suite that waited the default
10 minutes. Let's ensure that doesn't happen again.

* Add docs describing the cache mechanisms

* Replace CircleCI v1 notify with explicit curl

package.json

@@ -253,16 +253,13 @@
     "pretest": "npm run -s install-if-deps-outdated",
     "test": "run-s -s test-client test-server",
     "pretest-client": "npm run -s pretest",
-    "test-client": "jest -c=test/client/jest.config.json",
-    "test-client:ci": "cross-env-shell JEST_JUNIT_OUTPUT=./test-results-client.xml jest -c=test/client/jest.config.ci.js -w=2",
+    "test-client": "jest -c=test/client/jest.config.js",
     "test-client:watch": "npm run -s test-client -- --watch",
     "pretest-integration": "npm run -s pretest",
-    "test-integration": "jest -c=test/integration/jest.config.json",
-    "test-integration:ci": "cross-env-shell JEST_JUNIT_OUTPUT=./test-results-integration.xml jest -c=test/integration/jest.config.ci.js -w=2",
+    "test-integration": "jest -c=test/integration/jest.config.js",
     "test-integration:watch": "npm run -s test-integration -- --watch",
     "pretest-server": "npm run -s pretest",
-    "test-server": "jest -c=test/server/jest.config.json",
-    "test-server:ci": "cross-env-shell JEST_JUNIT_OUTPUT=./test-results-server.xml jest -c=test/server/jest.config.ci.js -w=2",
+    "test-server": "jest -c=test/server/jest.config.js",
     "test-server:coverage": "npm run -s test-server -- --coverage",
     "test-server:watch": "npm run -s test-server -- --watch",
     "translate": "i18n-calypso --format pot --output-file ./calypso-strings.pot -e date \"**/*.js\" \"**/*.jsx\" \"!build/**\" \"!node_modules/**\" \"!public/**\"",

test/client/jest.config.js

@@ -0,0 +1,23 @@
+/** @format */
+
+module.exports = {
+	moduleNameMapper: {
+		'^config$': '<rootDir>/server/config/index.js',
+	},
+	transform: {
+		'^.+\\.jsx?$': 'babel-jest',
+		'\\.(svg|(sc|sa|c)ss)$': '<rootDir>/test/test/helpers/assets/transform.js',
+	},
+	modulePaths: [ '<rootDir>/test/', '<rootDir>/client/', '<rootDir>/client/extensions/' ],
+	rootDir: './../../',
+	roots: [ '<rootDir>/client/' ],
+	testEnvironment: 'node',
+	transformIgnorePatterns: [ 'node_modules[\\/\\\\](?!flag-icon-css|redux-form)' ],
+	testMatch: [ '<rootDir>/client/**/test/*.js?(x)' ],
+	testURL: 'https://example.com',
+	setupTestFrameworkScriptFile: '<rootDir>/test/client/setup-test-framework.js',
+	verbose: false,
+	globals: {
+		google: {},
+	},
+};

test/client/setup-test-framework.js

@@ -1,7 +1,4 @@
-/**
- * @format
- */
-
+/** @format */
 /**
  * External dependencies
  */

test/integration/jest.config.js

@@ -0,0 +1,19 @@
+/** @format */
+
+module.exports = {
+	modulePaths: [
+		'<rootDir>/test/',
+		'<rootDir>/server/',
+		'<rootDir>/client/',
+		'<rootDir>/client/extensions/',
+	],
+	rootDir: './../../',
+	testEnvironment: 'node',
+	testMatch: [
+		'<rootDir>/bin/**/integration/*.js',
+		'<rootDir>/client/**/integration/*.js',
+		'<rootDir>/server/**/integration/*.js',
+		'<rootDir>/test/test/helpers/**/integration/*.js',
+	],
+	verbose: false,
+};

test/server/jest.config.js

@@ -0,0 +1,20 @@
+/** @format */
+
+module.exports = {
+	collectCoverageFrom: [ 'server/**/*.js?(x)' ],
+	coveragePathIgnorePatterns: [ '<rootDir>/server/devdocs/search-index.js' ],
+	modulePaths: [
+		'<rootDir>/test/',
+		'<rootDir>/server/',
+		'<rootDir>/client/',
+		'<rootDir>/client/extensions/',
+	],
+	rootDir: './../../',
+	roots: [ '<rootDir>/server/' ],
+	testEnvironment: 'node',
+	transformIgnorePatterns: [ 'node_modules[\\/\\\\](?!redux-form)' ],
+	testMatch: [ '<rootDir>/server/**/test/*.js?(x)' ],
+	timers: 'fake',
+	setupTestFrameworkScriptFile: '<rootDir>/test/server/setup-test-framework.js',
+	verbose: false,
+};

test/server/setup-test-framework.js

@@ -1,3 +1,4 @@
+/** @format */
 /**
  * External dependencies
  */