Test(infra): Add unit tests for backoff and sleep logic (Issue #4013)

src/infra/backoff.test.ts

@@ -0,0 +1,89 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { computeBackoff, sleepWithAbort } from "./backoff.js";
+
+describe("computeBackoff", () => {
+  const policy = {
+    initialMs: 1000,
+    maxMs: 10000,
+    factor: 2,
+    jitter: 0, // Disable jitter for deterministic tests unless specified
+  };
+
+  it("returns initialMs for the first attempt (attempt 1)", () => {
+    // attempt 1 => factor^(1-1) = factor^0 = 1
+    // 1000 * 1 = 1000
+    expect(computeBackoff(policy, 1)).toBe(1000);
+  });
+
+  it("returns calculated backoff for subsequent attempts", () => {
+    // attempt 2 => 1000 * 2^1 = 2000
+    expect(computeBackoff(policy, 2)).toBe(2000);
+    // attempt 3 => 1000 * 2^2 = 4000
+    expect(computeBackoff(policy, 3)).toBe(4000);
+  });
+
+  it("caps the backoff at maxMs", () => {
+    // attempt 10 => 1000 * 2^9 = 512000 > 10000
+    expect(computeBackoff(policy, 10)).toBe(10000);
+  });
+
+  it("treats attempt 0 or negative as attempt 1", () => {
+    expect(computeBackoff(policy, 0)).toBe(1000);
+    expect(computeBackoff(policy, -1)).toBe(1000);
+  });
+
+  it("applies jitter", () => {
+    const jitterPolicy = { ...policy, jitter: 0.5 }; // 50% jitter
+    // Base for attempt 2 is 2000.
+    // jitter = 2000 * 0.5 * Math.random() => [0, 1000]
+    // result = 2000 + [0, 1000] => [2000, 3000]
+
+    // We run it multiple times to ensure we get variance
+    const results = new Set();
+    for (let i = 0; i < 50; i++) {
+      const val = computeBackoff(jitterPolicy, 2);
+      results.add(val);
+      expect(val).toBeGreaterThanOrEqual(2000);
+      expect(val).toBeLessThanOrEqual(3000);
+    }
+    expect(results.size).toBeGreaterThan(1);
+  });
+});
+
+describe("sleepWithAbort", () => {
+  it("resolves after the specified duration", async () => {
+    vi.useFakeTimers();
+    const sleepPromise = sleepWithAbort(1000);
+
+    // Should not resolve yet
+    vi.advanceTimersByTime(500);
+
+    // Advance remaining time
+    vi.advanceTimersByTime(500);
+    await expect(sleepPromise).resolves.toBeUndefined();
+    vi.useRealTimers();
+  });
+
+  it("rejects immediately if abort signal is triggered", async () => {
+    const controller = new AbortController();
+    const sleepPromise = sleepWithAbort(5000, controller.signal);
+
+    controller.abort();
+
+    await expect(sleepPromise).rejects.toThrow("aborted");
+  });
+
+  it("rejects immediately if abort signal is already aborted", async () => {
+    const controller = new AbortController();
+    controller.abort();
+
+    const sleepPromise = sleepWithAbort(5000, controller.signal);
+    await expect(sleepPromise).rejects.toThrow("aborted");
+  });
+
+  it("resolves immediately for 0 or negative ms", async () => {
+    await expect(sleepWithAbort(0)).resolves.toBeUndefined();
+    await expect(sleepWithAbort(-100)).resolves.toBeUndefined();
+  });
+});