docs(AGENTS): add explicit preference against mocks; tests: remove mock usage in extensionManager.test.ts

- Document testing without mocks, prefer real IPC/processes and temp dirs
- Remove unused bun:test mock patterns from unit tests

_Generated with cmux_

Author: ammar-agent

docs/AGENTS.md

@@ -268,6 +268,30 @@ await env.mockIpcRenderer.invoke(IPC_CHANNELS.WORKSPACE_CREATE, projectPath, bra
 - Verifying filesystem state (like checking if files exist) after IPC operations complete
 - Loading existing data to avoid expensive API calls in test setup
 
+### Testing without Mocks (preferred)
+
+- Prefer exercising real behavior over substituting test doubles. Do not stub `child_process`, `fs`, or discovery logic.
+- Use temporary directories and real processes in unit tests where feasible. Clean up with `fs.rmSync(temp, { recursive: true, force: true })` in `afterEach`.
+- For extension system tests:
+  - Spawn the real global extension host via `ExtensionManager.initializeGlobal()`.
+  - Create real on-disk extensions in a temp `~/.cmux/ext` or project `.cmux/ext` folder.
+  - Register/unregister real workspaces and verify through actual tool execution.
+- Integration tests must go through real IPC. Use the test harness's `mockIpcRenderer.invoke()` to traverse the production IPC path (this is a façade, not a Jest mock).
+- Avoid spies and partial mocks. If a mock seems necessary, consider fixing the test harness or refactoring code to make the behavior testable without mocks.
+- Acceptable exceptions: isolating nondeterminism (e.g., time) or external network calls. Prefer dependency injection with in-memory fakes over broad module mocks.
+
+### Testing without Mocks (preferred)
+
+- Prefer exercising real behavior over substituting test doubles. Do not stub `child_process`, `fs`, or discovery logic.
+- Use temporary directories and real processes in unit tests where feasible. Clean up with `fs.rmSync(temp, { recursive: true, force: true })` in `afterEach`.
+- For extension system tests:
+  - Spawn the real global extension host via `ExtensionManager.initializeGlobal()`.
+  - Create real on-disk extensions in a temp `~/.cmux/ext` or project `.cmux/ext` folder.
+  - Register/unregister real workspaces and verify through actual tool execution.
+- Integration tests must go through real IPC. Use the test harness's `mockIpcRenderer.invoke()` to traverse the production IPC path (this is a façade, not a Jest mock).
+- Avoid spies and partial mocks. If a mock seems necessary, consider fixing the test harness or refactoring code to make the behavior testable without mocks.
+- Acceptable exceptions: isolating nondeterminism (e.g., time) or external network calls. Prefer dependency injection with in-memory fakes over broad module mocks.
+
 If IPC is hard to test, fix the test infrastructure or IPC layer, don't work around it by bypassing IPC.
 
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src/services/extensions/extensionManager.test.ts

@@ -1,29 +1,12 @@
 /* eslint-disable local/no-sync-fs-methods -- Test file uses sync fs for simplicity */
-/* eslint-disable @typescript-eslint/no-unsafe-assignment, @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-return, @typescript-eslint/no-explicit-any -- Mock setup requires any types */
-import { describe, test, beforeEach, afterEach, mock } from "bun:test";
+import { describe, test, beforeEach, afterEach } from "bun:test";
 import { ExtensionManager } from "./extensionManager";
 import type { WorkspaceMetadata } from "@/types/workspace";
 import type { RuntimeConfig } from "@/types/runtime";
-import { EventEmitter } from "events";
 import * as fs from "fs";
 import * as path from "path";
 import * as os from "os";
 
-// Mock child_process (not actually used in tests since we test the real thing)
-const mockChildProcess = {
-  fork: mock((_scriptPath: string, _options?: unknown) => {
-    const mockProcess = new EventEmitter() as any;
-    mockProcess.send = mock(() => true);
-    mockProcess.kill = mock(() => true);
-    mockProcess.killed = false;
-    mockProcess.stdout = new EventEmitter();
-    mockProcess.stderr = new EventEmitter();
-    return mockProcess;
-  }),
-};
-
-// Mock the discovery function (not actually used in tests)
-const mockDiscoverExtensions = mock(() => Promise.resolve([]));
 
 describe("ExtensionManager", () => {
   let manager: ExtensionManager;
@@ -33,9 +16,6 @@ describe("ExtensionManager", () => {
   let runtimeConfig: RuntimeConfig;
 
   beforeEach(() => {
-    // Reset all mocks
-    mockChildProcess.fork.mockClear();
-    mockDiscoverExtensions.mockClear();
 
     // Create temp directory for test
     tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "ext-mgr-test-"));