预计 spyOn 函数将被称为 Jest

Question

我目前正在尝试测试我创建的方法，并且我的 if 语句中的方法没有被调用。我完全不知所措。我是新人太开玩笑了，所以我确定我缺少一些简单的东西。

 describe('isSingleScreen', () => {
    beforeEach(() => {
      jest.clearAllMocks();
      jest.spyOn(utilMethods, 'isDualScreen').mockReturnValue(true);
    });

    it('autoScreenAdd', () => {
      // Arrange
      const singleScreenAddSpy = jest.spyOn(
        singleScreenMethods,
        'singleScreenAdd'
      );
      const dualScreenAddSpy = jest.spyOn(dualScreenMethods, 'dualScreenAdd');

      // Act
      utilMethods.autoScreenAdd({});

      // Assert
      expect(singleScreenAddSpy).toBeCalledTimes(0);
      expect(dualScreenAddSpy).toBeCalled();
      expect(dualScreenAddSpy).toBeCalledTimes(1);
    });
  });

export const isDualScreen = (): boolean => {
  return Dimensions.get('window').width > 1000 ? true : false;
};

export const autoScreenAdd = (element: IDualComponent) => {
  if (isDualScreen()) {
    dualScreenAdd(element);
  } else {
    singleScreenAdd(element);
  }
};

这是我收到的错误

    expect(jest.fn()).toBeCalledTimes(expected)

    Expected number of calls: 0
    Received number of calls: 1

      30 |       // Assert
      31 |       expect(autoScreenAddSpy).toBeCalled();
    > 32 |       expect(singleScreenAddSpy).toBeCalledTimes(0);
         |                                  ^
      33 |       expect(dualScreenAddSpy).toBeCalled();
      34 |       expect(dualScreenAddSpy).toBeCalledTimes(1);
      35 |     });

Answer 1

如何测试包含在同一模块中调用其他函数的函数的模块存在限制。 See this article for some more insight。在那篇文章中解决这个问题的方法很少，所以我建议在深入研究我的粗略实现之前先看看它，因为它可能无法 100% 使用你的代码结构。

工作示例：

CodesandBox

实用程序

对您的原始版本进行了轻微修改，因此您可能需要根据需要在您的 util 模块中进行模仿。

const isDualScreen = () => {
  return window.width > 1000 ? true : false;
};

const autoScreenAdd = element => {
  if (utilMethods.isDualScreen()) {
    utilMethods.dualScreenAdd(element);
  } else {
    utilMethods.singleScreenAdd(element);
  }
};

const dualScreenAdd = element => {
  return element;
};

const singleScreenAdd = element => {
  return element;
};

// This is important, it allows you to mock the functions properly in your tests.
// Use this same structure in your singleScreenMethods and dualScreenMethods modules
const utilMethods = {
  singleScreenAdd,
  dualScreenAdd,
  autoScreenAdd,
  isDualScreen
};

export default utilMethods;

测试示例

import utilMethods from "./utils";

describe("isSingleScreen", () => {
  beforeEach(() => {
    jest.clearAllMocks();
    jest.spyOn(utilMethods, "isDualScreen").mockReturnValue(true);
  });

  it("autoScreenAdd", () => {
    // Arrange
    const singleScreenAddSpy = jest.spyOn(utilMethods, "singleScreenAdd");
    const dualScreenAddSpy = jest.spyOn(utilMethods, "dualScreenAdd");

    // Act
    utilMethods.autoScreenAdd({});

    // Assert
    expect(singleScreenAddSpy).toHaveBeenCalledTimes(0);
    expect(dualScreenAddSpy).toHaveBeenCalledTimes(1);
  });
});