Question

我正在测试项目的功能之一，遇到一个奇怪的问题，我不知道如何解决此问题。

jest -v
24.8.0
node -v
v10.14.2

    const action = (fn1, fn2) => {
        fn1('fn1 call 1');

        return fn2('fn2 call 1')
            .then(() => {
                fn1('fn1 call 2');
                console.log('then was called');
            });
    };

    describe('test case', () => {
        it('should pass', () => {
            const fn1 = jest.fn();
            const fn2 = jest.fn()
                .mockResolvedValue(Promise.resolve('test'));

            action(fn1, fn2);

            expect(fn2).toBeCalledWith('fn2 call 1');
            expect(fn1).nthCalledWith(1,'fn1 call 1');
            expect(fn1).nthCalledWith(2,'fn1 call 2');
        })
    });

输出：

  ● test case › should pass

    expect(jest.fn()).nthCalledWith(expected)

    Expected mock function second call to have been called with:
      ["fn1 call 2"]
    But it was not called.

      19 |             expect(fn2).toBeCalledWith('fn2 call 1');
      20 |             expect(fn1).nthCalledWith(1,'fn1 call 1');
    > 21 |             expect(fn1).nthCalledWith(2,'fn1 call 2');
         |                         ^
      22 |         })
      23 |     });
      24 | 

      at Object.nthCalledWith (test.js:21:25)

  console.log test.js:7
    then was called

如果我将fn1替换为： (args) => console.log(args)

我明白了：

  console.log test.js:13
    fn1 call 1

  console.log test.js:13
    fn1 call 2

  console.log test.js:7
    then was called

因此，我使用jest.fn()的方式可能存在一些错误有人可以帮我解决这个问题吗？

Answer 1

您收到此错误的原因是fileInput返回了一个承诺，而您没有等待该承诺的结果；当第二次调用fileInput时，由于此行datapath而导致测试失败，因此会看到错误。另外，在action中调用fn1是多余的see doc

要解决此问题，您需要等待expect(fn1).nthCalledWith(2, 'fn1 call 2')的结果：

Promise.resolve('test')

另一种方法：

jest.fn().mockResolvedValue();

jest.fn（）模拟函数未第二次调用

1 个答案: