你如何编写一个 Jest 测试来检查代码执行是否被阻止？

Question

我正在使用async-mutex我只是想测试它的功能我想确认Mutex.acquire方法是否保持阻塞。

it('should remain blocked when accessing the mutex a second time', async () => {
    const mutex = new Mutex();
    const release = await mutex.acquire();
    expect(mutex.isLocked()).toBeTruthy();

    expect( async () => { await mutex.acquire() } ).toStillBeRunningAfterSpecifiedSeconds(5);
  });

我试过了

expect(await mutex.acquire()).toThrow("Timeout");

自从我收到这条消息

超时 - 在 jest.setTimeout.Timeout 指定的 5000 毫秒超时内未调用异步回调 - 在 jest.setTimeout.Error 指定的 5000 毫秒超时内未调用异步回调：

但没有运气。

Answer 1

这是您可以做到的一种方法：

describe("async-mutex", () => {
  it("checks that lock is released", (done) => {
    const mutex = new Mutex();

    // releases the lock right after locking it
    mutex.acquire().then((release) => {
      release();

      expect(mutex.isLocked()).toBe(false);

      done();
    });
  });

  it("checks that lock is not released", (done) => {
    // if test is running after 4 seconds, then mutex is still locked
    // done exits this test without errors
    setTimeout(() => {
      done();
    }, 4000);

    const mutex = new Mutex();

    mutex.acquire();

    expect(mutex.isLocked()).toBe(true);

    // this second call to acquire should never run
    // if it does, then the test should fail
    mutex.acquire().then(() => {
      expect(1).toBe(2);
    });
  });
});

现在，如果您的问题在于测试的持续时间，您可以随时使用jest.setTimeout(milliseconds)来增加它。