Migrate unit/integration tests to Vitest with Vite

As part of transition to Vue 3.0 and Vite (#230), this commit
facilitates the shift towards building rest of the application using
Vite. By doing so, it eliminates reliance on outdated Electron building
system that offered limited control, blocking desktop builds (#233).

Changes include:

- Introduce Vite with Vue 2.0 plugin for test execution.
- Remove `mocha`, `chai` and other related dependencies.
- Adjust test to Vitest syntax.
- Revise and update `tests.md` to document the changes.
- Add `@modyfi/vite-plugin-yaml` plugin to be able to use yaml file
  depended logic on test files, replacing previous webpack behavior.
- Fix failing tests that are revealed by Vitest due to unhandled errors
  and lack of assertments.
- Remove the test that depends on Vue CLI populating `process.env`.
- Use `jsdom` for unit test environment, adding it to dependency to
  `package.json` as project now depends on it and it was not specified
  even though `package-lock.json` included it.

package.json

@@ -9,7 +9,8 @@
   "scripts": {
     "serve": "vue-cli-service serve",
     "build": "vue-cli-service build",
-    "test:unit": "vue-cli-service test:unit --include ./tests/bootstrap/setup.ts",
+    "test:unit": "vitest run --dir tests/unit --environment jsdom",
+    "test:integration": "vitest run --dir tests/integration --environment node",
     "test:e2e": "vue-cli-service test:e2e",
     "lint": "npm run lint:md && npm run lint:md:consistency && npm run lint:md:relative-urls && npm run lint:eslint && npm run lint:yaml",
     "create-icons": "node img/logo-update.mjs",
@@ -21,8 +22,7 @@
     "lint:md:relative-urls": "remark . --frail --use remark-validate-links",
     "lint:yaml": "yamllint **/*.yaml --ignore=node_modules/**/*.yaml",
     "postinstall": "electron-builder install-app-deps",
-    "postuninstall": "electron-builder install-app-deps",
-    "test:integration": "vue-cli-service test:unit \"tests/integration/**/*.spec.ts\" --include ./tests/bootstrap/setup.ts"
+    "postuninstall": "electron-builder install-app-deps"
   },
   "main": "index.js",
   "dependencies": {
@@ -45,23 +45,21 @@
     "vue": "^2.7.14"
   },
   "devDependencies": {
+    "@modyfi/vite-plugin-yaml": "^1.0.4",
     "@rushstack/eslint-patch": "^1.3.2",
     "@types/ace": "^0.0.48",
-    "@types/chai": "^4.3.5",
     "@types/file-saver": "^2.0.5",
-    "@types/mocha": "^10.0.1",
     "@typescript-eslint/eslint-plugin": "^5.62.0",
     "@typescript-eslint/parser": "^5.62.0",
+    "@vitejs/plugin-vue2": "^2.2.0",
     "@vue/cli-plugin-babel": "~5.0.8",
     "@vue/cli-plugin-e2e-cypress": "~5.0.8",
     "@vue/cli-plugin-eslint": "~5.0.8",
     "@vue/cli-plugin-typescript": "~5.0.8",
-    "@vue/cli-plugin-unit-mocha": "~5.0.8",
     "@vue/cli-service": "~5.0.8",
     "@vue/eslint-config-airbnb-with-typescript": "^7.0.0",
     "@vue/eslint-config-typescript": "^11.0.3",
     "@vue/test-utils": "^1.3.6",
-    "chai": "^4.3.7",
     "cypress": "^12.17.2",
     "electron": "^25.3.2",
     "electron-builder": "^24.6.3",
@@ -75,6 +73,7 @@
     "eslint-plugin-vuejs-accessibility": "^1.2.0",
     "icon-gen": "^3.0.1",
     "js-yaml-loader": "^1.2.2",
+    "jsdom": "^22.1.0",
     "markdownlint-cli": "^0.35.0",
     "remark-cli": "^11.0.0",
     "remark-lint-no-dead-urls": "^1.1.0",
@@ -86,6 +85,8 @@
     "ts-loader": "^9.4.4",
     "tslib": "~2.4.0",
     "typescript": "~4.6.2",
+    "vite": "^4.4.9",
+    "vitest": "^0.34.2",
     "vue-cli-plugin-electron-builder": "^3.0.0-alpha.4",
     "yaml-lint": "^1.7.0"
   },