在Jest中使用toBeCalledWith（）测试参数

Question

我有使用puppetteer的page对象评估并返回一些数据的函数。

我想编写一个单元测试，jest以检查是否page.evaluate()采用了指定参数

这是功能

async function cinemasfromState(page, state) {
  const CINEMA_SELECTOR = `div[data-state=$[STATE]] div.top-select-option a.eccheckbox`;
  let res = await page.evaluate(
    (elementPath, state) => {
      let results = Array.from(document.querySelectorAll(elementPath)).map(
        function(cin, index) {
          return {
            //Stuff
          };
          return result;
        },
        { state }
      );
    },
    CINEMA_SELECTOR.replace("$[STATE]", state),
    state
  );

  return res;
}

以下是我的测试结果

describe("cinemasfromState", () => {
  let page_mock = {
    click: jest.fn(() => Promise.resolve()),
    evaluate: jest.fn((selector, state) => Promise.resolve())
  };

  test("page.evaluate called correctly ", async () => {
    await cinemasfromState(page_mock, "KAN");
    expect(page_mock.evaluate).toBeCalledTimes(1);
    expect(
      page_mock.evaluate)toBeCalledWith(
        "div[data-state=KAN] div.top-select-option a.eccheckbox",
        "KAN"
      );
  });
});

我得到以下错误作为我的测试输出

? cinemasfromState › page.evaluate called correctly

    expect(jest.fn()).toBeCalledWith(expected)

    Expected mock function to have been called with:
      "div[data-state=KAN] div.top-select-option a.eccheckbox"
    as argument 1, but it was called with
      [Function anonymous].

    Difference:

      Comparing two different types of values. Expected string but received function.
      "KAN"
    as argument 2, but it was called with
      "div[data-state=KAN] div.top-select-option a.eccheckbox".
      undefined
    as argument 3, but it was called with
      "KAN".

    Difference:

      Comparing two different types of values. Expected undefined but received string.

      52 |     expect(page_mock1.evaluate).toBeCalledTimes(1);
      53 |     expect(page_mock1.evaluate).toBeCalledWith(
    > 54 |       "div[data-state=KAN] div.top-select-option a.eccheckbox",
         |                            ^
      55 |       "KAN"
      56 |     );
      57 |   });

对编写测试以验证参数有帮助吗？

Answer 1

如果阅读错误日志，您会注意到它正在尝试匹配三个参数，但是您只针对两个参数进行了断言。.toBeCalledWith在开玩笑的情况下，将对传递给函数的参数及其顺序进行精确匹配。

例如，如果您调用func(arg1, arg2)，expect(func).toBeCalledWith(arg2)则会失败，因为您未同时声明on arg1。这就是您的情况，因为to的第一个参数page.evaluate()实际上是一个匿名函数。

因此，您的测试将需要如下所示：

expect(page_mock.evaluate).toBeCalledWith(
  expect.any(Function),
  "div[data-state=KAN] div.top-select-option a.eccheckbox",
  "KAN"
);