chore(testing): slim testing/ to only what can't be colocated

package.json

@@ -23,9 +23,6 @@
     "package:mac": "electron-builder --mac --publish never",
     "dist:mac": "npm run build && npm run package:mac",
     "start": "electron-vite preview",
-    "testing:rendering": "npm run testing:rendering:build && electron testing/rendering/out/main/main.js",
-    "testing:rendering:build": "electron-vite build --config testing/rendering/electron.vite.config.ts",
-    "testing:rendering:preview": "electron testing/rendering/out/main/main.js",
     "test": "NODE_ENV=test vitest run",
     "test:watch": "NODE_ENV=test vitest",
     "test:unit": "NODE_ENV=test vitest run --project unit",

testing/unit/workspace/applyPromptSuggestionToRuntime.test.ts → src/renderer/src/workspace/hook/ipc/applyPromptSuggestionToRuntime.test.ts

@@ -59,11 +59,10 @@ describe('provider session identity helpers', () => {
   it('keeps jsonl-entry and legacy provider ids resumable', () => {
     expect(hasDurableProviderSession(durableMeta)).toBe(true)
     expect(resumableProviderSessionId(durableMeta)).toBe('durable-1')
-    expect(hasDurableProviderSession({
-      cwd: '/repo',
-      kind: 'claude',
-      providerSessionId: 'legacy-1',
-    })).toBe(true)
+    // hasDurableProviderSession only reads providerSessionId / *IdSource, so
+    // pass exactly that Pick — the old {cwd,kind,…} extras were untyped noise
+    // that the web tsconfig now (rightly) rejects once this test is colocated.
+    expect(hasDurableProviderSession({ providerSessionId: 'legacy-1' })).toBe(true)
   })
 
   it('upgrades a proxy-header id when JSONL confirms the same provider session', () => {

testing/README.md

@@ -1,27 +1,38 @@
-# Agent Code Test Suite
+# Agent Code Test Infrastructure
 
-This directory holds shared test infrastructure, fixtures, and manual harnesses.
-Normal tests should live beside the production module they protect whenever
-that makes ownership obvious.
+Tests live **beside the production module they protect** (`foo.ts` →
+`foo.test.ts`). This directory is only for the few things that *can't* be
+colocated:
+
+- **`fixtures/`** — the rendering corpus (`rendering-bundles/`,
+  `rendering-recordings/`) replayed by `src/renderer/src/rendering/bundleCorpus.test.ts`
+  and `recordingCorpus.test.ts`. The regression net for the rendering pipeline.
+- **`setup/renderer.ts`** — happy-dom setup file for the `renderer` Vitest project.
+- **`unit/channels/`, `unit/proxy/`** — tests for `packages/claude-code-headless`
+  (a git submodule). They live here because a test file can't be colocated
+  *inside* a submodule from this repo.
+
+Everything else — pure functions, reducers, selectors, mappers, ledgers,
+components — is colocated under `src/`. If you're reaching for `testing/` for a
+new test, it almost certainly belongs next to its source instead.
 
 ## Commands
 
 ```bash
-npm test
+npm test              # all projects
 npm run test:unit
 npm run test:integration
 npm run test:renderer
 ```
 
-## Test Layers
+## Projects (see `vitest.config.ts`)
 
-- `unit`: pure functions, reducers, selectors, mappers, ownership ledgers.
-- `integration`: multiple Node/app modules wired together without Electron.
-- `renderer`: React component tests in `happy-dom`.
+- `unit` — node env: `src/**/*.test.ts`, `packages/**`, `testing/unit/**`
+- `integration` — node env: `**/*.integration.test.ts`
+- `renderer` — happy-dom: `**/*.renderer.test.{ts,tsx}` (+ `testing/setup/renderer.ts`)
 
 ## Policy
 
-Do not add new `scripts/test-*.ts` files. The old script tests were useful as
-incident probes, but they are not the project test architecture. New coverage
-belongs in Vitest.
-
+Do not add `scripts/test-*.ts` files — the old script tests were incident
+probes, not the test architecture. New coverage is a Vitest file next to its
+source.