retry.spec.ts

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],
        ],
      ]
    `);
  });
});