test(process): replace no-output timer subprocess with spawn mock

src/process/exec.no-output-timer.test.ts

@@ -0,0 +1,73 @@
+import type { ChildProcess } from "node:child_process";
+import { EventEmitter } from "node:events";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+const spawnMock = vi.hoisted(() => vi.fn());
+
+vi.mock("node:child_process", async () => {
+  const actual = await vi.importActual<typeof import("node:child_process")>("node:child_process");
+  return {
+    ...actual,
+    spawn: spawnMock,
+  };
+});
+
+import { runCommandWithTimeout } from "./exec.js";
+
+function createFakeSpawnedChild() {
+  const child = new EventEmitter() as EventEmitter & ChildProcess;
+  const stdout = new EventEmitter();
+  const stderr = new EventEmitter();
+  let killed = false;
+  const kill = vi.fn<(signal?: NodeJS.Signals) => boolean>(() => {
+    killed = true;
+    return true;
+  });
+  Object.defineProperty(child, "killed", {
+    get: () => killed,
+    configurable: true,
+  });
+  Object.defineProperty(child, "pid", {
+    value: 12345,
+    configurable: true,
+  });
+  child.stdout = stdout as ChildProcess["stdout"];
+  child.stderr = stderr as ChildProcess["stderr"];
+  child.stdin = null;
+  child.kill = kill as ChildProcess["kill"];
+  return { child, stdout, stderr, kill };
+}
+
+describe("runCommandWithTimeout no-output timer", () => {
+  afterEach(() => {
+    vi.useRealTimers();
+    vi.restoreAllMocks();
+  });
+
+  it("resets no-output timeout when spawned child keeps emitting stdout", async () => {
+    vi.useFakeTimers();
+    const fake = createFakeSpawnedChild();
+    spawnMock.mockReturnValue(fake.child);
+
+    const runPromise = runCommandWithTimeout(["node", "-e", "ignored"], {
+      timeoutMs: 1_000,
+      noOutputTimeoutMs: 80,
+    });
+
+    fake.stdout.emit("data", Buffer.from("."));
+    await vi.advanceTimersByTimeAsync(40);
+    fake.stdout.emit("data", Buffer.from("."));
+    await vi.advanceTimersByTimeAsync(40);
+    fake.stdout.emit("data", Buffer.from("."));
+    await vi.advanceTimersByTimeAsync(20);
+
+    fake.child.emit("close", 0, null);
+    const result = await runPromise;
+
+    expect(result.code ?? 0).toBe(0);
+    expect(result.termination).toBe("exit");
+    expect(result.noOutputTimedOut).toBe(false);
+    expect(result.stdout).toBe("...");
+    expect(fake.kill).not.toHaveBeenCalled();
+  });
+});

src/process/exec.test.ts

@@ -56,38 +56,6 @@ describe("runCommandWithTimeout", () => {
     expect(result.code).not.toBe(0);
   });
 
-  it("resets no output timer when command keeps emitting output", async () => {
-    const result = await runCommandWithTimeout(
-      [
-        process.execPath,
-        "-e",
-        [
-          "let count = 0;",
-          "const emit = () => {",
-          'process.stdout.write(".");',
-          "count += 1;",
-          "if (count >= 4) {",
-          "process.exit(0);",
-          "return;",
-          "}",
-          "setTimeout(emit, 40);",
-          "};",
-          "emit();",
-        ].join(" "),
-      ],
-      {
-        timeoutMs: 2_000,
-        // Keep a healthy margin above the emit interval for loaded CI runners.
-        noOutputTimeoutMs: 400,
-      },
-    );
-
-    expect(result.code ?? 0).toBe(0);
-    expect(result.termination).toBe("exit");
-    expect(result.noOutputTimedOut).toBe(false);
-    expect(result.stdout.length).toBeGreaterThanOrEqual(3);
-  });
-
   it("reports global timeout termination when overall timeout elapses", async () => {
     const result = await runCommandWithTimeout(
       [process.execPath, "-e", "setTimeout(() => {}, 10)"],