✅ add a Jasmine to Vitest codemod and a migration guard

Groundwork to migrate specs from the Jasmine API to the Vitest API in small
PRs, without blocking other work (unmigrated specs keep running through the
Jasmine compatibility shim).

- scripts/test/jasmine-to-vitest.ts: deterministic codemod (TypeScript AST,
  in-place text edits, Prettier) converting spies, spy strategies, calls,
  matchers, asymmetric matchers, done callbacks, pending(), fail(), focus/
  skip and types; constructs it can't convert safely are reported. On a
  conflict, take the file from main and re-run it.
- eslint.config.ts: VITEST_API_SPEC_FILES, where Jasmine globals are
  forbidden and test functions must be imported from 'vitest'
- vitest declared as a devDependency of every workspace with specs
- AGENTS.md: write new specs with the Vitest API
- remove the unused mockContextManager helper

Author: thomas-lebeau

AGENTS.md

@@ -102,6 +102,7 @@ For deeper context, see:
 
 - Test framework: Jasmine API on Vitest Browser Mode (via a shim in `test/unit-vitest/`). Spec files co-located with implementation: `feature.ts` → `feature.spec.ts`
 - Focus tests with `fit()` / `fdescribe()`, skip with `xit()` / `xdescribe()`
+- Specs are being migrated from the Jasmine API to the Vitest API. Write new specs with the Vitest API (`import { describe, expect, it, vi } from 'vitest'`), unless they depend on a test helper that still returns Jasmine spies. Convert existing specs with `node scripts/test/jasmine-to-vitest.ts <files or directories>`, fix what it reports, then add the paths to `VITEST_API_SPEC_FILES` in `eslint.config.ts`
 - Use `registerCleanupTask()` for cleanup, NOT `afterEach()`
 - Prefer `collectAsyncCalls(spy, n)` over `waitFor(() => spy.calls.count() > 0)` for waiting on spy calls
 - Don't destructure methods from `spy.calls` (e.g., `argsFor`, `mostRecent`) - use `calls.argsFor()` to avoid `@typescript-eslint/unbound-method` errors

developer-extension/package.json

@@ -12,7 +12,8 @@
     "@types/react-dom": "19.3.0",
     "@wxt-dev/module-react": "1.2.2",
     "typescript": "6.0.3",
-    "vite": "8.3.2"
+    "vite": "8.3.2",
+    "vitest": "4.1.8"
   },
   "dependencies": {
     "@datadog/browser-core": "workspace:*",

eslint.config.ts

@@ -1,5 +1,6 @@
 import eslint from '@eslint/js'
 import { defineConfig } from 'eslint/config'
+import type { Linter } from 'eslint'
 import * as tseslint from 'typescript-eslint'
 import { importX } from 'eslint-plugin-import-x'
 import unicornPlugin from 'eslint-plugin-unicorn'
@@ -12,6 +13,28 @@ import eslintLocalRules from './eslint-local-rules/index.ts'
 import { SCHEMAS } from './scripts/lib/generatedSchemaTypes.ts'
 
 const SPEC_FILES = '**/*.{spec,specHelper}.{ts,tsx,js}'
+// Spec files migrated from the Jasmine API to the Vitest API (see scripts/test/jasmine-to-vitest.ts).
+// Add the migrated paths here so the Jasmine API doesn't come back.
+const VITEST_API_SPEC_FILES: string[] = []
+const JASMINE_GLOBALS = [
+  'jasmine',
+  'spyOn',
+  'spyOnProperty',
+  'fail',
+  'pending',
+  'expectAsync',
+  'fdescribe',
+  'fit',
+  'xdescribe',
+  'xit',
+]
+// Provided as globals by the Jasmine compatibility shim: migrated files import them from 'vitest'
+const SHIM_TEST_GLOBALS = ['describe', 'it', 'expect', 'beforeEach', 'afterEach', 'beforeAll', 'afterAll']
+const NO_JASMINE_GLOBALS_RULE: Linter.RuleEntry = [
+  'error',
+  ...JASMINE_GLOBALS.map((name) => ({ name, message: 'Use the Vitest API instead of the Jasmine API.' })),
+  ...SHIM_TEST_GLOBALS.map((name) => ({ name, message: `Import \`${name}\` from 'vitest'.` })),
+]
 const PUBLIC_PACKAGE_ENTRIES = 'packages/{browser-rum,browser-logs,browser-rum-slim}/src/entries/*.ts'
 const MONITOR_UNTIL_COMMENT_EXPIRED_LEVEL =
   (process.env.MONITOR_UNTIL_COMMENT_EXPIRED_LEVEL as 'warn' | 'error' | undefined) || 'warn'
@@ -524,5 +547,16 @@ export default defineConfig(
         },
       ],
     },
-  }
+  },
+
+  ...(VITEST_API_SPEC_FILES.length
+    ? [
+        {
+          files: VITEST_API_SPEC_FILES,
+          rules: {
+            'no-restricted-globals': NO_JASMINE_GLOBALS_RULE,
+          },
+        },
+      ]
+    : [])
 )

packages/browser-core/test/mockGlobalContext.ts

@@ -19,7 +19,8 @@
     "prepack": "yarn build"
   },
   "devDependencies": {
-    "acorn": "8.19.0"
+    "acorn": "8.19.0",
+    "vitest": "4.1.8"
   },
   "dependencies": {
     "@datadog/browser-core": "workspace:*",

packages/browser-debugger/package.json

@@ -40,5 +40,8 @@
   },
   "publishConfig": {
     "access": "public"
+  },
+  "devDependencies": {
+    "vitest": "4.1.8"
   }
 }

packages/browser-logs/package.json

@@ -46,5 +46,8 @@
   },
   "publishConfig": {
     "access": "public"
+  },
+  "devDependencies": {
+    "vitest": "4.1.8"
   }
 }

packages/browser-plugin-wasm/package.json

@@ -43,6 +43,7 @@
     "@angular/core": "22.2.1",
     "@angular/platform-browser": "22.2.1",
     "@angular/router": "22.2.1",
-    "rxjs": "7.8.2"
+    "rxjs": "7.8.2",
+    "vitest": "4.1.8"
   }
 }

packages/browser-rum-angular/package.json

@@ -21,7 +21,8 @@
     "@datadog/js-core": "workspace:*"
   },
   "devDependencies": {
-    "ajv": "8.20.0"
+    "ajv": "8.20.0",
+    "vitest": "4.1.8"
   },
   "repository": {
     "type": "git",

packages/browser-rum-core/package.json

@@ -46,6 +46,7 @@
     "@types/react": "19.3.0",
     "next": "16.3.8",
     "react": "19.3.0",
-    "react-dom": "19.3.0"
+    "react-dom": "19.3.0",
+    "vitest": "4.1.8"
   }
 }