开玩笑地模拟回调或嵌套函数

Question

I have code as,

public async waitForElementSelected(element: WebdriverIO.Element) {
    /**
     * Maximum number of milliseconds to wait for
     * @type {Int}
     */
    const ms = 10000;
    await browser.waitUntil(async () =>{
      return element.isSelected();
    },{
      timeout: ms,
      timeoutMsg: 'Condition not met: Element is not selected',
      interval: 100
    });
  }

Here, I have easily tested wait until by mocking the browser, but I am not able to mock "isSelected" or element.isSelected(); line.

I have tried, mocking

global.element = {
      isSelected: jest.fn()
    };

But it is not working as expected, and giving element.isSelected() line still under not covered.

Following is my Test case,

    describe('waitForElementToBeSelected', () => {
  beforeEach(() => {
    mockElement = {
      isSelected: jest.fn()
    };
    mockElement.isSelected.mockReturnValue(true);

    /** **browser mock section ***/
    // global.browser = {
    //   waitUntil: ()=> {
    //     mockElement.isSelected();
    //   }
    // };
  });

  it('should call waitForElementSelected on the browser object', async () => {
    await waitActions.waitForElementToBeSelected(mockElement);
    expect(mockElement.isSelected).toHaveBeenCalled();
    // 
//expect(global.browser.waitUntil).toHaveBeenCalledTimes(1);
  });
});

This code is giving me the error, "browser not defined". If I enabled the code,/** **browser mock section ***/ then, I am getting that, line

return element.isSelected()

is still not getting covered.

Answer 1

This is because element is not a global variable, but an argument that you are passing into the waitForElementSelected function. What you need to do instead is pass an object with mock functions when calling it.

So in your test you can have it as follows:

// mock out the element
const mockElement = {
  isSelected: jest.fn()
};

// mock out the promise response
mockElement.isSelected.mockReturnValue(new Promise((resolve) => resolve(true)));

// call the function
waitForElementSelected(mockElement);

// expect
expect(mockElement.isSelected).toHaveBeenCalled();