feat!: update jest to v26 (#6116)

closes #5873
closes #5874
closes #5114
closes #5680
closes #5573

docs/migrations/migrate-from-v4.md

@@ -101,6 +101,12 @@ Please consider switching to ESLint. You can check out [`tslint-to-eslint-config
 * Cypress is required as a peer dependency.
 * Cypress is updated from v3 to v5. See [Cypress Migration Guide](https://docs.cypress.io/guides/references/migration-guide.html) for detailed instructions of the migration process.
 
+### Unit-Jest Plugin
+
+* The underlying `jest`-related packages are upgraded from v24 to v26. For most users the transition would be seamless. See their corresponding changelogs for more detail:
+  * [jest, babel-jest](https://github.com/facebook/jest/blob/v26.6.3/CHANGELOG.md)
+  * [ts-jest](https://github.com/kulshekhar/ts-jest/blob/v26.4.4/CHANGELOG.md)
+
 ### Unit-Mocha Plugin
 
 * `mocha` is upgraded from v6 to v7, please refer to the [release notes of mocha v7](https://github.com/mochajs/mocha/releases/tag/v7.0.0) for a complete list of breaking changes.

package.json

@@ -47,7 +47,7 @@
     "@vuepress/plugin-pwa": "^1.5.4",
     "@vuepress/theme-vue": "^1.5.4",
     "babel-core": "7.0.0-bridge.0",
-    "babel-jest": "^24.9.0",
+    "babel-jest": "^26.6.3",
     "chromedriver": "^87.0.0",
     "debug": "^4.1.0",
     "eslint": "^7.13.0",
@@ -65,7 +65,7 @@
     "graphql": "^14.6.0",
     "http-server": "^0.12.3",
     "inquirer": "^7.1.0",
-    "jest": "^24.9.0",
+    "jest": "^26.6.3",
     "lerna": "^3.22.0",
     "lerna-changelog": "^1.0.1",
     "lint-staged": "^9.5.0",

packages/@vue/cli-plugin-typescript/package.json

@@ -46,7 +46,7 @@
   },
   "devDependencies": {
     "@types/chai": "^4.2.11",
-    "@types/jest": "^24.0.19",
+    "@types/jest": "^26.0.16",
     "@types/mocha": "^7.0.2",
     "jscodeshift": "^0.10.0",
     "typescript": "~3.9.3",

packages/@vue/cli-plugin-unit-jest/package.json

@@ -25,18 +25,17 @@
   "dependencies": {
     "@babel/core": "^7.11.6",
     "@babel/plugin-transform-modules-commonjs": "^7.9.6",
-    "@types/jest": "^24.0.19",
+    "@types/jest": "^26.0.16",
     "@vue/cli-shared-utils": "^4.5.8",
     "babel-core": "^7.0.0-bridge.0",
-    "babel-jest": "^24.9.0",
+    "babel-jest": "^26.6.3",
     "babel-plugin-transform-es2015-modules-commonjs": "^6.26.2",
     "deepmerge": "^4.2.2",
-    "jest": "^24.9.0",
-    "jest-environment-jsdom-fifteen": "^1.0.2",
+    "jest": "^26.6.3",
     "jest-serializer-vue": "^2.0.2",
     "jest-transform-stub": "^2.0.0",
     "jest-watch-typeahead": "^0.4.2",
-    "ts-jest": "^24.2.0",
+    "ts-jest": "^26.4.4",
     "vue-jest": "^3.0.5"
   },
   "devDependencies": {

packages/@vue/cli-plugin-unit-jest/presets/default/jest-preset.js

@@ -18,7 +18,6 @@ module.exports = {
   moduleNameMapper: {
     '^@/(.*)$': '<rootDir>/src/$1'
   },
-  testEnvironment: 'jest-environment-jsdom-fifteen',
   // serializer for snapshots
   snapshotSerializers: [
     'jest-serializer-vue'