test(lib): make idle deadline reset timing deterministic

tests/lib/abort-idle-deadline.test.ts

@@ -1,4 +1,4 @@
-import { expect, test } from "bun:test";
+import { expect, spyOn, test } from "bun:test";
 import { idleDeadline } from "../../src/lib/abort";
 
 const sleep = (ms: number) => new Promise(resolve => setTimeout(resolve, ms));
@@ -17,18 +17,59 @@ test("idleDeadline fires once after the idle window with no reset", async () =>
   expect(fired).toBe(1);
 });
 
-test("idleDeadline reset() re-arms and postpones firing", async () => {
+test("idleDeadline reset() re-arms and postpones firing", () => {
+  // Keep this boundary check synchronous: real sleeps can resume after the idle window.
+  // The other cases below still exercise Bun's real timers.
+  type TimerHandle = ReturnType<typeof setTimeout>;
+  let now = 0;
+  let nextHandle = 0;
+  const timers = new Map<TimerHandle, { at: number; fire: () => void }>();
+  const timeoutSpy = spyOn(globalThis, "setTimeout").mockImplementation(((
+    callback: (...args: unknown[]) => void, delay = 0, ...args: unknown[]
+  ) => {
+    const handle = ++nextHandle as unknown as TimerHandle;
+    timers.set(handle, { at: now + delay, fire: () => callback(...args) });
+    return handle;
+  }) as typeof setTimeout);
+  const clearSpy = spyOn(globalThis, "clearTimeout").mockImplementation(handle => {
+    timers.delete(handle as TimerHandle);
+  });
+  const advanceBy = (ms: number) => {
+    const target = now + ms;
+    for (;;) {
+      const due = [...timers].filter(([, timer]) => timer.at <= target)
+        .sort((a, b) => a[1].at - b[1].at)[0];
+      if (!due) break;
+      timers.delete(due[0]);
+      now = due[1].at;
+      due[1].fire();
+    }
+    now = target;
+  };
   let fired = 0;
-  const idle = idleDeadline(120, () => { fired += 1; });
-  idle.reset();
-  for (let i = 0; i < 4; i++) {
-    await sleep(40);
-    idle.reset(); // keep-alive: total elapsed (160ms) exceeds 120ms but silence never does
+  let idle: ReturnType<typeof idleDeadline> | undefined;
+  try {
+    idle = idleDeadline(120, () => { fired += 1; });
+    idle.reset();
+    for (let i = 0; i < 4; i++) {
+      advanceBy(40);
+      idle.reset(); // total elapsed exceeds 120 ms, but each silent interval does not
+    }
+    expect(fired).toBe(0);
+    advanceBy(119);
+    expect(fired).toBe(0);
+    advanceBy(1);
+    expect(fired).toBe(1);
+    advanceBy(240);
+    expect(fired).toBe(1);
+  } finally {
+    try {
+      idle?.cancel();
+    } finally {
+      clearSpy.mockRestore();
+      timeoutSpy.mockRestore();
+    }
   }
-  expect(fired).toBe(0);
-  await sleep(220);
-  expect(fired).toBe(1);
-  idle.cancel();
 });
 
 test("idleDeadline pause() disarms without retiring; reset() re-arms after pause", async () => {