Jest mock 无法拾取错误抛出？答案

【问题标题】：Jest mock unnable to pick up error throw?Jest mock 无法拾取错误抛出？
【发布时间】：2020-05-22 12:12:36
【问题描述】：

我有一些调用 api 的代码。我正在测试嵌套在 try catch 中的功能，并在我抛出具有某些值的错误时检查正确的行为。

async function createDeployment(namespace, config, name) {
  try {
    await k8sDeploymentApi.createNamespacedDeployment(namespace, config, true);
    console.log('Successful deployment');
    return Promise.resolve(true);
  } catch (e) {
    console.log(JSON.stringify(e));
    if (e.response.statusCode === HTTP_CONFLICT) {
      try {
        await k8sDeploymentApi.replaceNamespacedDeployment(name, namespace, config, true);
        console.log('Successfully replaced deployment');
        return Promise.resolve(true);
      } catch (error) {
        return Promise.reject(error);
      }
    }
    return Promise.reject(e);
  }
}

我在这里模拟 api 调用节点模块

var mockListNamespacedIngress;
var mockCreateNamespacedDeployment;
var mockReplaceNamespacedDeployment;
jest.mock('@kubernetes/client-node', () => {
  mockListNamespacedIngress = jest.fn();
  mockCreateNamespacedDeployment = jest.fn();
  mockReplaceNamespacedDeployment = jest.fn();
  return {
    KubeConfig: jest.fn().mockImplementation(() => ({
      loadFromCluster: jest.fn(),
      loadFromDefault: jest.fn(),
      makeApiClient: () => ({
        listNamespacedIngress: mockListNamespacedIngress,
        createNamespacedDeployment: mockCreateNamespacedDeployment,
        replaceNamespacedDeployment: mockReplaceNamespacedDeployment,
      }),
    })),
  };
});

并在此处运行测试

    it.only('Should return a log of success if replaced deployment resolves', async () => {
      mockCreateNamespacedDeployment.mockRejectedValueOnce(() =>
        Promise.reject(new Error({ response: { statusCode: 409 } })),
      );

      mockReplaceNamespacedDeployment.mockResolvedValueOnce(true);

      // When
      await expect(createDeployment()).resolves.toEqual(true);
    });

但是，在 console.log(JSON.stringify(e)) 上，我只会得到未定义的返回。所以它似乎确实抛出了错误，但没有从 catch 中给出错误对象。这是我的完整堆栈跟踪

 ● Kubernetes deployment script tests › Kubernetes Calls › Should return a log of success if replaced deployment resolves

    expect(received).resolves.toEqual()

    Received promise rejected instead of resolved
    Rejected to value: [TypeError: Cannot read property 'statusCode' of undefined]

      143 |
      144 |       // When
    > 145 |       await expect(createDeployment()).resolves.toEqual(true);
          |             ^
      146 |     });
      147 |   });
      148 |

      at expect (node_modules/expect/build/index.js:134:15)
      at Object.it.only (src/__tests__/index.test.js:145:13)

  console.log
    Successful deployment

      at createDeployment (src/index.js:73:13)

  console.log
    undefined

      at createDeployment (src/index.js:76:13)

【问题讨论】：

标签： javascript unit-testing mocking jestjs

【解决方案1】：

你可以像这样模拟一个抛出错误的异步函数

mockCreateNamespacedDeployment.mockRejectedValueOnce(new Error({ response: { statusCode: 409 } });

然后你可以期待

await expect(createDeployment()).rejects.toThrow();

顺便说一句，在您的 async 函数中，您可以替换所有的

- Promise.resolve(xxx)
+ return xxx

// and
- Promise.reject(xxx)
+ throw xxx

【讨论】：

当我这样做时，我仍然得到'成功部署'的console.log，并且在catch（e）中创建的'e'变量中没有值，而不是当我正常运行代码时，当 createNamespacedDeployment 错误并带有 409 http 状态码时，它会中断。