期望在反应测试库中使用参数调用 jest mock 失败

Question

我希望这个测试通过，但它失败了：

it('should consume files on drop', () => {
  const mock = jest.fn();
  const file = new File(['file'], 'file.txt', { type: 'text/plain' });
  const fileList = [file];

  render(<DropZone onDocumentDrop={mock} />);

  const dropZone = screen.getByTestId('dropZone');
  const dropEvent = createEvent.drop(dropZone);

  Object.defineProperty(dropEvent, 'dataTransfer', {
    value: {
      files: {
        item: (index: number) => fileList[index],
        length: fileList.length,
      },
    },
  });

  fireEvent(dropZone, dropEvent);

  expect(dropZone).toBeInTheDocument();
  expect(mock).toHaveBeenCalled();
  expect(mock).toHaveBeenCalledWith({
    item: (index: number) => fileList[index],
    length: 1,
  });
});

Jest 报告说：

expect(jest.fn()).toHaveBeenCalledWith(...expected)

- Expected
+ Received

- {"item": [Function item], "length": 1},
+ {"item": [Function item], "length": 1},

我不知道如何让它通过或深入了解出了什么问题？

Answer 1

当检查最后一个函数调用的参数时，可以使用expect.objectContaining()来匹配接收到的对象。

您也可以使用lastCalledWith()代替toHaveBeenCalledWith(). 它们是相同的，但我个人更喜欢前者，因为它更短且更容易阅读。

const item = (index: number) => []
const args = {
  length: 1,
  item,
}

const mock = jest.fn()

mock(args)

expect(mock).lastCalledWith(
  expect.objectContaining({
    length: expect.any(Number), // or 1 if you know the exact value
    item: expect.any(Function),
  })
)