我如何用 throw e 开玩笑地进行测试? [英] How I can test in jest line with throw e?

问题描述

我如何在玩笑错误情况下进行测试?这就是我所做的:我不知道是否存在一种方法来测试这个.

How I can test in jest error case? This is what I do: I don't know if exist a method how to test this.

it ('the fetch fails and throw an error', async () => {
      let response = {
        status: 400,
        body: 
        {
          base : "RON",
          date: "2019-08-01",
          rates: {"error": 'error'}
        }
      };
      fetch.mockReject(response)
      try {
        await fetchData();
      } catch (e) {
        expect(e).toEqual(response);
        expect(await fetchData()).rejects.toThrow(e);
      }
    });

这是代码:

 fetchData = async () => {
    try {
      const response = await fetch('https://api.exo/latest?base=RON');
      const data = await response.json();
      return data;
    } catch (e) {
      throw e;
    }
  };

推荐答案

expect.assertions 救援

it ('the fetch fails and throw an error', async () => {
  expect.assertions(1);
  let response = {
    status: 400,
    body: {
      base : "RON",
      date: "2019-08-01",
      rates: {"error": 'error'}
    }
  };
  fetch.mockReject(response)
  try {
    await fetchData();
  } catch (e) {
    expect(e).toEqual(response);
  }
});

一旦没有异常抛出，测试就会失败.它比 expect().toThrown 有优势:

Test will fail once no exception is thrown. It has advantages over expect().toThrown:

1. 您不必在 it() 中返回 Promise 即可使其工作
2. 更容易断言多个相关异常或顺序操作失败
3. 在捕获的错误上运行部分匹配更容易(比如使用 expect(e).toMatchObject({}) 跳过一些你在当前测试用例中不关心的数据)

1. you don't have to return Promise in your it() to make it work
2. it's easier to assert several related exceptions or sequential actions failed
3. it's easier to run partial matching over error caught(say with expect(e).toMatchObject({}) to skip some data you don't care about in current test case)

至于缺点 - 添加新断言后必须手动更新编号

As for disadvantages - you have to update number manually after adding new assertions

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