feat: Install and configure jest

Author: CGNonofr

.eslintrc.js

@@ -1,7 +1,8 @@
 module.exports = {
   env: {
     browser: true,
-    es6: true
+    es6: true,
+    jest: true
   },
   extends: [
     'standard'

babel.test.config.js

@@ -0,0 +1,11 @@
+module.exports = {
+  plugins: [
+    ["@babel/plugin-transform-modules-commonjs", {
+      importInterop: 'babel'
+    }]
+  ],
+  presets: [
+    "@babel/preset-env",
+    "@babel/preset-typescript"
+  ]
+};

browserMock.js

@@ -0,0 +1,52 @@
+const fs = require('fs/promises')
+
+Object.defineProperty(document, 'queryCommandSupported', {
+  value: jest.fn().mockImplementation(() => true),
+});
+
+Object.defineProperty(window, 'matchMedia', {
+  writable: true,
+  value: jest.fn().mockImplementation(query => ({
+    matches: false,
+    media: query,
+    onchange: null,
+    addListener: jest.fn(), // Deprecated
+    removeListener: jest.fn(), // Deprecated
+    addEventListener: jest.fn(),
+    removeEventListener: jest.fn(),
+    dispatchEvent: jest.fn(),
+  })),
+});
+
+Object.defineProperty(window, 'fetch', {
+  value: jest.fn(async (path) => {
+
+    const content = await fs.readFile(path)
+    return {
+      json: async () => JSON.stringify(JSON.parse(content.toString())),
+      arrayBuffer: async () => content.buffer.slice(content.byteOffset, content.byteOffset + content.byteLength)
+    }
+  })
+})
+
+Object.defineProperty(URL, 'createObjectURL', {
+  value: jest.fn((blob) => {
+
+    return null
+  })
+})
+
+Object.defineProperty(window, 'Worker', {
+  value: class Worker {
+    constructor(stringUrl) {}
+    postMessage(msg) {}
+    terminate () {}
+  }
+})
+
+Object.defineProperty(window, 'ResizeObserver', {
+  value: class ResizeObserver {
+    constructor(stringUrl) {}
+    observe() {}
+  }
+})

jest/cssTransform.js

@@ -0,0 +1,14 @@
+'use strict';
+
+// This is a custom Jest transformer turning style imports into empty objects.
+// http://facebook.github.io/jest/docs/en/webpack.html
+
+module.exports = {
+  process() {
+    return 'module.exports = {};';
+  },
+  getCacheKey() {
+    // The output is always the same.
+    return 'cssTransform';
+  },
+};

jest/fileTransform.js

@@ -0,0 +1,7 @@
+module.exports = {
+  process(src, filename) {
+    const assetFilename = JSON.stringify(filename);
+
+    return `module.exports = ${assetFilename};`;
+  },
+};

package.json

@@ -4,7 +4,9 @@
   "private": false,
   "description": "Enhanced Monaco editor with TextMate grammars and more",
   "scripts": {
-    "build": "rollup --config rollup.config.ts --configPlugin typescript && npm run generate-types",
+    "test": "npx jest",
+    "test:watch": "jest --watch",
+    "build": "npm run test && rollup --config rollup.config.ts --configPlugin typescript && npm run generate-types",
     "prepublishOnly": "npm run build",
     "generate-types": "tsc --project tsconfig.types.json && rollup --config rollup.types.config.ts --configPlugin typescript && rm -rf ./dist/types"
   },
@@ -31,6 +33,7 @@
     "@babel/core": "7.17.7",
     "@babel/plugin-proposal-class-properties": "7.16.7",
     "@babel/plugin-proposal-optional-chaining": "7.16.7",
+    "@babel/plugin-transform-modules-commonjs": "^7.17.7",
     "@babel/preset-env": "7.16.11",
     "@babel/preset-typescript": "7.16.7",
     "@babel/runtime": "7.17.7",
@@ -41,6 +44,7 @@
     "@rollup/plugin-json": "4.1.0",
     "@rollup/plugin-node-resolve": "13.1.3",
     "@rollup/plugin-typescript": "^8.3.1",
+    "@types/jest": "^27.4.1",
     "@types/once": "^1.4.0",
     "@types/rollup-plugin-node-builtins": "^2.1.2",
     "@types/vscode": "^1.65.0",
@@ -51,9 +55,11 @@
     "eslint-config-standard": "17.0.0-1",
     "eslint-config-standard-jsx": "11.0.0-1",
     "eslint-plugin-import": "2.25.4",
+    "eslint-plugin-jest": "^26.1.1",
     "eslint-plugin-node": "11.1.0",
     "eslint-plugin-promise": "6.0.0",
     "eslint-plugin-unused-imports": "2.0.0",
+    "jest": "^27.5.1",
     "monaco-languageclient": "^0.18.0",
     "proxy-polyfill": "^0.3.2",
     "rollup": "2.70.1",
@@ -76,6 +82,33 @@
     "not IE 11",
     "not IE_Mob 11"
   ],
+  "jest": {
+    "testEnvironment": "jest-environment-jsdom",
+    "modulePathIgnorePatterns": [
+      "<rootDir>/dist/"
+    ],
+    "setupFiles": [
+      "<rootDir>/browserMock.js"
+    ],
+    "transformIgnorePatterns": [
+      "^.+\\.module\\.(css|sass|scss)$"
+    ],
+    "transform": {
+      "^(?!.*\\.(js|ts|css|json)$)": "<rootDir>/jest/fileTransform.js",
+      "^.+\\.css$": "<rootDir>/jest/cssTransform.js",
+      "^.+\\.(js|ts)$": [
+        "<rootDir>/node_modules/babel-jest",
+        {
+          "configFile": "./babel.test.config.js"
+        }
+      ]
+    },
+    "moduleNameMapper": {
+      "^vscode$": "monaco-languageclient/lib/vscode-compatibility",
+      "^monaco-editor$": "monaco-editor/esm/vs/editor/edcore.main",
+      "^monaco-editor-core$": "monaco-editor/esm/vs/editor/edcore.main"
+    }
+  },
   "volta": {
     "node": "16.14.0",
     "npm": "8.5.0"