update jest.config.js to include additional path ignores and add semver and underscore dependencies

.github/workflows/unit-tests.yml

@@ -5,7 +5,6 @@ on:
     paths:
       - 'tools/**'
       - 'scripts/**'
-      - 'jest.config.js'
       - 'package.json'
       - '.github/workflows/unit-tests.yml'
   push:
@@ -30,8 +29,8 @@ jobs:
         with:
           node-version: 22.x
 
-      - name: Install deps
-        run: npm install
+      - name: Install unit test deps
+        run: npm run install:unit
 
       - name: Run unit tests
         run: npm run test:unit

DEVELOPMENT.md

@@ -128,17 +128,20 @@ The repository has four test layers, each covering a different scope:
 
 ### Unit tests (Jest)
 
-Unit tests cover pure helpers, scripts, and tool logic that does not require the Meteor runtime. They use [Jest](https://jestjs.io/) configured at the monorepo root (`jest.config.js`), targeting `tools/**/*.test.js` and `scripts/**/*.test.js`.
+Unit tests cover pure helpers, scripts, and tool logic that does not require the Meteor runtime. They use [Jest](https://jestjs.io/) configured in `tools/unit-tests/`, targeting `tools/**/*.test.js` and `scripts/**/*.test.js`.
 
 ```sh
+# Install dependencies (first time)
+npm run install:unit
+
 # Run all unit tests
 npm run test:unit
 
 # Run a specific test file
-npx jest tools/path/to/file.test.js
+npm run test:unit -- tools/path/to/file.test.js
 
 # Run tests matching a name pattern
-npx jest -t "my test name"
+npm run test:unit -- -t "my test name"
 ```
 
 Place test files next to the module they test using the `*.test.js` naming convention. Jest will pick them up automatically.

package.json

@@ -16,8 +16,6 @@
     "@babel/eslint-parser": "^7.21.3",
     "@babel/eslint-plugin": "^7.19.1",
     "@babel/preset-react": "^7.18.6",
-    "@swc/core": "^1.15.18",
-    "@swc/jest": "^0.2.39",
     "@types/lodash.isempty": "^4.4.9",
     "@types/node": "^18.16.18",
     "@types/sockjs": "^0.3.36",
@@ -33,14 +31,12 @@
     "eslint-plugin-prettier": "^4.2.1",
     "eslint-plugin-react": "^7.32.2",
     "eslint-plugin-react-hooks": "^4.6.0",
-    "jest": "^30.2.0",
     "prettier": "^2.8.8",
-    "semver": "^7.7.2",
-    "typescript": "^5.4.5",
-    "underscore": "^1.13.7"
+    "typescript": "^5.4.5"
   },
   "scripts": {
-    "test:unit": "jest --config jest.config.js --passWithNoTests",
+    "install:unit": "cd tools/unit-tests && npm install",
+    "test:unit": "cd tools/unit-tests && npm test",
     "test:idle-bot": "node --test .github/scripts/__tests__/inactive-issues.test.js",
     "install:e2e": "cd tools/modern-tests && npm install && npx playwright install --with-deps chromium chromium-headless-shell",
     "test:e2e": "cd tools/modern-tests && npm test -- "

tools/modern-tests/README.md

@@ -0,0 +1,20 @@
+# E2E Tests
+
+Isolated Jest + Playwright environment for end-to-end testing Meteor skeletons and bundler integrations.
+
+The repo root `node_modules/` is used to build the dev bundle, which becomes the Meteor tool itself. Installing test deps (jest, playwright, swc, cheerio, semver, underscore) there could pull in incompatible transitive versions (e.g. lru-cache v10 vs v5) and silently break the dev bundle build or a published Meteor release. This subfolder keeps test dependencies fully isolated so they never affect how Meteor is built or shipped.
+
+Tests create real Meteor projects, start dev servers, and assert behavior in a headless Chromium browser.
+
+All commands below should be run from the repo root:
+
+```sh
+# Install dependencies (first time)
+npm run install:e2e
+
+# Run all E2E tests
+npm run test:e2e
+
+# Run a specific suite
+npm run test:e2e -- --testPathPattern skeleton
+```

tools/modern-tests/package.json

@@ -1,7 +1,7 @@
 {
   "name": "meteor-modern-tests",
   "version": "1.0.0",
-  "description": "Modern tests for Meteor",
+  "description": "Isolated Jest + Playwright environment for Meteor E2E tests",
   "scripts": {
     "test": "jest --config jest.config.js"
   },

tools/unit-tests/README.md

@@ -0,0 +1,23 @@
+# Unit Tests
+
+Isolated Jest environment for unit-testing Meteor `tools/` and `scripts/`.
+
+The repo root `node_modules/` is used to build the dev bundle, which becomes the Meteor tool itself. Installing test deps (jest, swc, semver, underscore) there could pull in incompatible transitive versions (e.g. lru-cache v10 vs v5) and silently break the dev bundle build or a published Meteor release. This subfolder keeps test dependencies fully isolated so they never affect how Meteor is built or shipped.
+
+Test files use `*.test.js` next to their source.
+
+All commands below should be run from the repo root:
+
+```sh
+# Install dependencies (first time)
+npm run install:unit
+
+# Run all unit tests
+npm run test:unit
+
+# Run a specific test file
+npm run test:unit -- tools/path/to/file.test.js
+
+# Run tests matching a name pattern
+npm run test:unit -- -t "my test name"
+```

tools/unit-tests/jest.config.js

@@ -1,5 +1,9 @@
+const path = require('path');
+
+const repoRoot = path.resolve(__dirname, '../..');
+
 module.exports = {
-  rootDir: __dirname,
+  rootDir: repoRoot,
   testMatch: [
     "<rootDir>/tools/**/*.test.js",
     "<rootDir>/scripts/**/*.test.js",
@@ -20,6 +24,9 @@ module.exports = {
     "<rootDir>/docs/",
     "<rootDir>/packages/non-core/",
   ],
+  modulePaths: [
+    path.resolve(__dirname, 'node_modules'),
+  ],
   transform: {
     "^.+\\.js$": ["@swc/jest", {
       jsc: {

tools/unit-tests/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "meteor-unit-tests",
+  "version": "1.0.0",
+  "private": true,
+  "description": "Isolated Jest environment for Meteor unit tests",
+  "scripts": {
+    "test": "jest --config jest.config.js --passWithNoTests"
+  },
+  "devDependencies": {
+    "@swc/core": "^1.15.18",
+    "@swc/jest": "^0.2.39",
+    "jest": "^30.2.0",
+    "semver": "^7.7.2",
+    "underscore": "^1.13.7"
+  }
+}