开玩笑：如何将参数传递给模拟构造函数？

Question

如果我想创建 ES6 类的实例方法的模拟实现，我会这样做

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// ExampleClass.js\nexport class ExampleClass {\n    constructor(someValue) {\n        this.a = someValue;\n    }\n\n    exampleMethod(anotherValue) {\n        // do something with \'anotherValue\'\n    }\n}\n\n// OtherModule.js\nimport {ExampleClass} from \'./ExampleClass\';\nexport const fooBar = () => {\n    const ex = new ExampleClass("hello world");\n    ex.exampleMethod("another value");\n};\n\n// ExampleClass.test.js\nimport {fooBar} from \'./OtherModule\';\nimport {ExampleClass} from \'./ExampleClass\';\njest.mock(\'./ExampleClass\');\n\nit(\'try to create a mock of ExampleClass\', () => {\n    ExampleClass.mockClear();\n\n    fooBar();\n\n    // to verify values for of instance method "exampleMethod" of ExampleClass instance\n    expect(ExampleClass.mock.instances[0].exampleMethod.calls.length).toBe(1);\n    expect(ExampleClass.mock.instances[0].exampleMethod.calls[0][0]).toBe("another value");\n\n    // How to verify values for **constructor** of ExampleClass ?????\n    // expect(ExampleClass.mock.instances[0].constructor.calls.length).toBe(1);\n    // expect(ExampleClass.mock.instances[0].constructor.calls[0][0]).toBe("another value");\n});\n

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我不知道该怎么做（以及在注释代码中提到的）是如何监视/访问构造函数的值（而不仅仅是实例方法）。

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任何帮助将不胜感激！\xe2\x9d\xa4

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Answer 1

ExampleClass 是构造函数，由于整个模块是自动模拟的，因此它已经设置为模拟函数：

import {fooBar} from './OtherModule';
import {ExampleClass} from './ExampleClass';
jest.mock('./ExampleClass');

it('try to create a mock of ExampleClass', () => {
    ExampleClass.mockClear();

    fooBar();

    // to verify values for of instance method "exampleMethod" of ExampleClass instance
    expect(ExampleClass.mock.instances[0].exampleMethod.mock.calls.length).toBe(1);  // SUCCESS
    expect(ExampleClass.mock.instances[0].exampleMethod.mock.calls[0][0]).toBe("another value");  // SUCCESS

    // Verify values for **constructor** of ExampleClass
    expect(ExampleClass.mock.calls.length).toBe(1);  // SUCCESS
    expect(ExampleClass.mock.calls[0][0]).toBe("hello world");  // SUCCESS
});