Question

查看Jest问题和SO answers后，我尝试了以下4个选项，但我遇到TypeScript错误或运行时错误。我真的很想让选项1（spyOn）工作。

// ------ option 1 -----
// Gives this runtime error: "Cannot spyOn on a primitive value; undefined given"
const writeText = jest.spyOn(navigator.clipboard, 'writeText');

// ------ option 2 -----
Object.defineProperty(navigator, 'clipboard', {
    writeText: jest.fn(),
});

// ------ option 3 -----
// This is from SO answer but gives a TypeScript error
window.__defineGetter__('navigator', function() {
    return {
        clipboard: {
            writeText: jest.fn(x => x)
        }
    }
})

// ------ option 4 -----
const mockClipboard = {
    writeText: jest.fn()
};
global.navigator.clipboard = mockClipboard;

Answer 1

Jest测试是在JSdom环境中运行的，并不是所有的属性都已定义，但是您应该在监视该函数之前先定义它。

这里是一个例子：

Object.assign(navigator, {
  clipboard: {
    writeText: () => {},
  },
});

describe("Clipboard", () => {
  describe("writeText", () => {
    jest.spyOn(navigator.clipboard, "writeText");
    beforeAll(() => {
      yourImplementationThatWouldInvokeClipboardWriteText();
    });
    it("should call clipboard.writeText", () => {
      expect(navigator.clipboard.writeText).toHaveBeenCalledWith("zxc");
    });
  });
});

编辑：您也可以使用Object.defineProperty，但是它接受描述符对象作为第三个参数

Object.defineProperty(navigator, "clipboard", {
  value: {
    writeText: () => {},
  },
});

Answer 2

我遇到了类似的情况，使用以下方法模拟导航器对象中的剪贴板：

  const originalClipboard = { ...global.navigator.clipboard };
  const mockData = {
     "name": "Test Name",
     "otherKey": "otherValue"
  }

  beforeEach(() => {
    const mockClipboard = {
      writeText: jest.fn(),
    };
    global.navigator.clipboard = mockClipboard;

  });

  afterEach(() => {
    jest.resetAllMocks();
    global.navigator.clipboard = originalClipboard;
  });

  test("copies data to the clipboard", () => {
    copyData(); //my method in the source code which uses the clipboard
    expect(navigator.clipboard.writeText).toBeCalledTimes(1);
    expect(navigator.clipboard.writeText).toHaveBeenCalledWith(
      JSON.stringify(mockData)
    );
  });

如何在Jest中模拟navigator.clipboard.writeText（）？

2 个答案: