chore: update to jest 27 (#811)

* chore: update to jest 27

Updates jest, ts-jest and babel-jest to v27.
vue-jest v5 does not support jest v27,
so a new vue3-jest package has been introduced (see vuejs/vue-jest#343),
with a version number aligned on the jest version (as ts-jest and babel-jest do).

This commits replaces vue-jest by vue3-jest, and updates the jest config to use this new trasnformer.
This will be the default Vue CLI setup in the future.

* chore: document hasOwnProperty Jest workaround

Author: cexbrayat

jest.config.js

@@ -12,7 +12,7 @@ module.exports = {
   },
   testEnvironment: 'jsdom',
   transform: {
-    '^.+\\.vue$': 'vue-jest',
+    '^.+\\.vue$': '@vue/vue3-jest',
     '^.+\\js$': 'babel-jest'
   },
   moduleFileExtensions: ['vue', 'js', 'json', 'jsx', 'ts', 'tsx', 'node'],

package.json

@@ -26,10 +26,11 @@
     "@vue/compat": "3.2.31",
     "@vue/compiler-dom": "3.2.31",
     "@vue/compiler-sfc": "3.2.31",
-    "babel-jest": "^26.6.3",
-    "babel-preset-jest": "^27.5.1",
+    "@vue/vue3-jest": "27.0.0-alpha.4",
+    "babel-jest": "27.1.0",
+    "babel-preset-jest": "27.0.6",
     "husky": "^7.0.4",
-    "jest": "25.5.4",
+    "jest": "27.5.1",
     "jsdom": "^19.0.0",
     "jsdom-global": "^3.0.2",
     "lint-staged": "^12.3.3",
@@ -38,7 +39,7 @@
     "reflect-metadata": "^0.1.13",
     "rollup": "^2.67.2",
     "rollup-plugin-typescript2": "^0.31.2",
-    "ts-jest": "25.3.1",
+    "ts-jest": "27.1.3",
     "tslib": "2.3.1",
     "typescript": "4.5.5",
     "vitepress": "^0.22.0",

src/mount.ts

@@ -507,7 +507,8 @@ export function mount(
   console.warn = () => {}
 
   const appRef = vm.$refs[MOUNT_COMPONENT_REF] as ComponentPublicInstance
-  // we add `hasOwnProperty` so jest can spy on the proxied vm without throwing
+  // we add `hasOwnProperty` so Jest can spy on the proxied vm without throwing
+  // note that this is not necessary with Jest v27+ or Vitest, but is kept for compatibility with older Jest versions
   appRef.hasOwnProperty = (property) => {
     return Reflect.has(appRef, property)
   }