Jest preset: Add default jest preset for WordPress development (#74)

* Jest preset: Add default jest preset for WordPress developmnent

* Jest preset: Use path to jest preset relative to root directory

package.json

@@ -6,6 +6,7 @@
 	},
 	"devDependencies": {
 		"@wordpress/browserslist-config": "^2.0.0",
+		"@wordpress/jest-preset-default": "^1.0.0",
 		"babel-core": "^6.26.0",
 		"chalk": "^2.0.1",
 		"check-node-version": "^3.1.1",
@@ -19,11 +20,7 @@
 		"collectCoverageFrom": [
 			"packages/*/**/*.js"
 		],
-		"coveragePathIgnorePatterns": [
-			"<rootDir>/.*/build.*"
-		],
-		"coverageDirectory": "coverage",
-		"setupTestFrameworkScriptFile": "./packages/jest-console/build/index.js"
+		"preset": "./node_modules/@wordpress/jest-preset-default/jest-preset.json"
 	},
 	"scripts": {
 		"build-clean": "rimraf ./packages/*/build ./packages/*/build-module",

packages/jest-preset-default/README.md

@@ -0,0 +1,47 @@
+# @wordpress/jest-preset-default
+
+Default [Jest](https://facebook.github.io/jest/) preset for WordPress development.
+
+## Installation
+
+Install the module
+
+```bash
+npm install @wordpress/jest-preset-default --save-dev
+```
+
+## Setup
+
+### Via jest.config.json or `jest` field in `package.json`
+
+```json
+{
+  "preset": "@wordpress/jest-preset-default"
+}
+```
+
+### Usage
+
+#### Brief explanations of options included
+
+* `coverageDirectory` - the directory where Jest outputs its coverage files is set to `coverage`.
+* `coveragePathIgnorePatterns` - coverage information will be skipped for all folders named `build` and `build-module`.
+* `moduleNameMapper` - all `css` and `scss` files containing CSS styles will be stubbed out.
+* `modulePaths` - the root dir of the project is used as a location to search when resolving modules.
+* `setupFiles` - runs code before each test which sets up global variables required in the testing environment.
+* `setupTestFrameworkScriptFile` - runs code which adds improved support for `Console` object and `React` components to the testing framework before each test.
+* `testMatch`- includes `/test/` subfolder in the glob patterns Jest uses to detect test files. It detects only test files containing `.js` extension.
+* `timers` - use of [fake timers](https://facebook.github.io/jest/docs/en/timer-mocks.html) for functions such as `setTimeout` is enabled.
+* `transform` - adds support for [PEG.js]( https://github.com/pegjs/pegjs#javascript-api) transformed necessary for WordPress blocks. It also keeps the default [babel-jest](https://github.com/facebook/jest/tree/master/packages/babel-jest) transformer.
+* `verbose` - each individual test won't be reported during the run.
+
+#### Overriding `setupTestFrameworkScriptFile`
+
+It is also possible to override the script that runs some code to configure or set up the testing framework before each test. To do so you will need to create `setup-test-framework.js` inside your project with the following content:
+
+```js
+// You can still load the default script provided by this setup
+import '@wordpress/jest-preset-default';
+
+// Your code goes here
+```

packages/jest-preset-default/index.js

@@ -0,0 +1 @@
+module.exports = require( './scripts/setup-test-framework' );

packages/jest-preset-default/jest-preset.json

@@ -0,0 +1,29 @@
+{
+	"coverageDirectory": "coverage",
+	"coveragePathIgnorePatterns": [
+		"/node_modules/",
+		"<rootDir>/.*/build/",
+		"<rootDir>/.*/build-module/"
+	],
+	"moduleNameMapper": {
+		"\\.(scss|css)$": "<rootDir>/node_modules/@wordpress/jest-preset-default/scripts/style-mock.js"
+	},
+	"modulePaths": [
+		"<rootDir>"
+	],
+	"setupFiles": [
+		"<rootDir>/node_modules/@wordpress/jest-preset-default/scripts/setup-globals.js"
+	],
+	"setupTestFrameworkScriptFile": "<rootDir>/node_modules/@wordpress/jest-preset-default/scripts/setup-test-framework.js",
+	"testMatch": [
+		"**/__tests__/**/*.js",
+		"**/?(*.)(spec|test).js",
+		"**/test/*.js"
+	],
+	"timers": "fake",
+	"transform": {
+		"^.+\\.jsx?$": "babel-jest",
+		"\\.pegjs$": "<rootDir>/node_modules/@wordpress/jest-preset-default/scripts/pegjs-transform.js"
+	},
+	"verbose": true
+}