Add tests for the retry utility

assets/js/utils/__tests__/retry.spec.ts

@@ -0,0 +1,216 @@
+import { mockDateNow, mockRandom } from '../../../test/mock';
+import { retry, RetryFunc, RetryParams } from '../retry';
+
+describe('retry', () => {
+  async function expectRetry<R>(params: RetryParams, maybeFunc?: RetryFunc<R>) {
+    const func = maybeFunc ?? (() => Promise.reject(new Error('always failing')));
+    const spy = vi.fn(func);
+
+    // Preserve the empty name of the anonymous functions. Spy wrapper overrides it.
+    const funcParam = func.name === '' ? (...args: Parameters<RetryFunc<R>>) => spy(...args) : spy;
+
+    const promise = retry(funcParam, params).catch(err => `throw ${err}`);
+
+    await vi.runAllTimersAsync();
+    const result = await promise;
+
+    const retries = spy.mock.calls.map(([attempt, nextDelayMs]) => {
+      const suffix = nextDelayMs === undefined ? '' : 'ms';
+      return `${attempt}: ${nextDelayMs}${suffix}`;
+    });
+
+    return expect([...retries, result]);
+  }
+
+  // Remove randomness and real delays from the tests.
+  mockRandom();
+  mockDateNow(0);
+
+  const consoleErrorSpy = vi.spyOn(console, 'error');
+
+  afterEach(() => {
+    consoleErrorSpy.mockClear();
+  });
+
+  describe('stops on a successful attempt', () => {
+    it('first attempt', async () => {
+      (await expectRetry({}, async () => 'ok')).toMatchInlineSnapshot(`
+        [
+          "1: 200ms",
+          "ok",
+        ]
+      `);
+    });
+    it('middle attempt', async () => {
+      const func: RetryFunc<'ok'> = async attempt => {
+        if (attempt !== 2) {
+          throw new Error('middle failure');
+        }
+        return 'ok';
+      };
+
+      (await expectRetry({}, func)).toMatchInlineSnapshot(`
+        [
+          "1: 200ms",
+          "2: 300ms",
+          "ok",
+        ]
+      `);
+    });
+    it('last attempt', async () => {
+      const func: RetryFunc<'ok'> = async attempt => {
+        if (attempt !== 3) {
+          throw new Error('last failure');
+        }
+        return 'ok';
+      };
+
+      (await expectRetry({}, func)).toMatchInlineSnapshot(`
+        [
+          "1: 200ms",
+          "2: 300ms",
+          "3: undefined",
+          "ok",
+        ]
+      `);
+    });
+  });
+
+  it('produces a reasonable retry sequence within maxAttempts', async () => {
+    (await expectRetry({})).toMatchInlineSnapshot(`
+      [
+        "1: 200ms",
+        "2: 300ms",
+        "3: undefined",
+        "throw Error: always failing",
+      ]
+    `);
+
+    (await expectRetry({ maxAttempts: 5 })).toMatchInlineSnapshot(`
+      [
+        "1: 200ms",
+        "2: 300ms",
+        "3: 600ms",
+        "4: 1125ms",
+        "5: undefined",
+        "throw Error: always failing",
+      ]
+    `);
+  });
+
+  it('turns into a fixed delay retry algorithm if min/max bounds are equal', async () => {
+    (await expectRetry({ maxAttempts: 3, minDelayMs: 200, maxDelayMs: 200 })).toMatchInlineSnapshot(`
+      [
+        "1: 200ms",
+        "2: 200ms",
+        "3: undefined",
+        "throw Error: always failing",
+      ]
+    `);
+  });
+
+  it('allows for zero delay', async () => {
+    (await expectRetry({ maxAttempts: 3, minDelayMs: 0, maxDelayMs: 0 })).toMatchInlineSnapshot(`
+      [
+        "1: 0ms",
+        "2: 0ms",
+        "3: undefined",
+        "throw Error: always failing",
+      ]
+    `);
+  });
+
+  describe('fails on first non-retryable error', () => {
+    it('all errors are retryable', async () => {
+      (await expectRetry({ isRetryable: () => false })).toMatchInlineSnapshot(`
+        [
+          "1: 200ms",
+          "throw Error: always failing",
+        ]
+      `);
+    });
+    it('middle error is non-retriable', async () => {
+      const func: RetryFunc<never> = async attempt => {
+        if (attempt === 3) {
+          throw new Error('non-retryable');
+        }
+        throw new Error('retryable');
+      };
+
+      const params: RetryParams = {
+        isRetryable: error => error.message === 'retryable',
+      };
+
+      (await expectRetry(params, func)).toMatchInlineSnapshot(`
+        [
+          "1: 200ms",
+          "2: 300ms",
+          "3: undefined",
+          "throw Error: non-retryable",
+        ]
+      `);
+    });
+  });
+
+  it('rejects invalid inputs', async () => {
+    (await expectRetry({ maxAttempts: 0 })).toMatchInlineSnapshot(`
+      [
+        "throw Error: Invalid 'maxAttempts' for retry: 0",
+      ]
+    `);
+    (await expectRetry({ minDelayMs: -1 })).toMatchInlineSnapshot(`
+      [
+        "throw Error: Invalid 'minDelayMs' for retry: -1",
+      ]
+    `);
+    (await expectRetry({ maxDelayMs: 100 })).toMatchInlineSnapshot(`
+      [
+        "throw Error: Invalid 'maxDelayMs' for retry: 100, 'minDelayMs' is 200",
+      ]
+    `);
+  });
+
+  it('should use the provided label in logs', async () => {
+    (await expectRetry({ label: 'test-routine' })).toMatchInlineSnapshot(`
+      [
+        "1: 200ms",
+        "2: 300ms",
+        "3: undefined",
+        "throw Error: always failing",
+      ]
+    `);
+
+    expect(consoleErrorSpy.mock.calls).toMatchInlineSnapshot(`
+      [
+        [
+          "All 3 attempts of running test-routine failed",
+          [Error: always failing],
+        ],
+      ]
+    `);
+  });
+
+  it('should use the function name in logs', async () => {
+    async function testFunc() {
+      throw new Error('always failing');
+    }
+
+    (await expectRetry({}, testFunc)).toMatchInlineSnapshot(`
+      [
+        "1: 200ms",
+        "2: 300ms",
+        "3: undefined",
+        "throw Error: always failing",
+      ]
+    `);
+
+    expect(consoleErrorSpy.mock.calls).toMatchInlineSnapshot(`
+      [
+        [
+          "All 3 attempts of running testFunc failed",
+          [Error: always failing],
+        ],
+      ]
+    `);
+  });
+});