sinon 监视回调答案

【问题标题】：sinon spying on callbackssinon 监视回调
【发布时间】：2020-05-23 02:39:25
【问题描述】：

我觉得我大致了解 sinon 的工作原理，但我在监视传递给我正在测试的导入函数的回调时遇到了一些麻烦。这是一个例子：

import sinon from 'sinon'

const callbackCaller = (cb: (msg:string) => void, msg: string) => {
    cb(`CallbackCaller called with ${cb}, ${msg}`)
}

describe('This seems wrong', () => {
    it('should pass but doesn\'t', () => {
        const callback = (msg: string) => {
            console.log(`Callback called with ${msg}`)
        }

        const callbackSpy = sinon.spy(callback)

        callbackCaller(callback, 'tarfu')
        sinon.assert.called(callbackSpy)
    })
})

运行时，此测试按预期打印，但断言失败：

$ yarn test:failure

yarn run v1.21.1
$ jest src/test.test.ts
 FAIL  src/test.test.ts
  This seems wrong
    ✕ should pass but doesn't (8ms)

  ● This seems wrong › should pass but doesn't

    AssertError: expected callback to have been called at least once but was never called

      14 | 
      15 |         callbackCaller(callback, 'tarfu')
    > 16 |         sinon.assert.called(callbackSpy)
         |                      ^
      17 |     })
      18 | })
      19 | 

      at Object.fail (../../../node_modules/sinon/lib/sinon/assert.js:107:21)
      at failAssertion (../../../node_modules/sinon/lib/sinon/assert.js:66:16)
      at Object.assert.(anonymous function) [as called] (../../../node_modules/sinon/lib/sinon/assert.js:92:13)
      at Object.it (test.test.ts:16:22)

  console.log src/test.test.ts:10
    Callback called with CallbackCaller called with (msg) => {
                console.log(`Callback called with ${msg}`);
            }, tarfu

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 total
Snapshots:   0 total
Time:        0.815s, estimated 1s
Ran all test suites matching /src\/test.test.ts/i.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

请注意，回调确实被调用了，正如它打印在堆栈跟踪下方所证明的那样。我正在使用节点版本 10.16 和 jest 25.1.0。由于回调是在失败后记录的，所以看起来开玩笑是在 callbackCaller 调用 cb 之前检查间谍，但没有异步的东西，所以我有点不知所措。希望解决方案不是“sinon 不使用其他工具”:)

【问题讨论】：

标签： javascript typescript unit-testing jestjs sinon

【解决方案1】：

您应该将callbackSpy 传递给callbackCaller 函数，而不是原来的callback。因为sinon 用 spy(callbacksSpy) 包装了callback，所以你可以使用sinon.assert.called 来断言它。

index.test.ts:

import sinon from 'sinon';

const callbackCaller = (cb: (msg: string) => void, msg: string) => {
  cb(`CallbackCaller called with ${cb}, ${msg}`);
};

describe('This seems wrong', () => {
  it("should pass but doesn't", () => {
    const callback = (msg: string) => {
      console.log(`Callback called with ${msg}`);
    };

    const callbackSpy = sinon.spy(callback);

    callbackCaller(callbackSpy, 'tarfu');
    sinon.assert.called(callbackSpy);
  });
});

单元测试结果：

This seems wrong
Callback called with CallbackCaller called with callback, tarfu
    ✓ should pass but doesn't


  1 passing (6ms)

【讨论】：