即使函数已被调用，expect(jest.fn()).toHaveBeenCalled() 也会失败答案

【问题标题】：expect(jest.fn()).toHaveBeenCalled() fails even though the function has been called即使函数已被调用，expect(jest.fn()).toHaveBeenCalled() 也会失败
【发布时间】：2021-05-16 17:48:54
【问题描述】：

我正在尝试对返回承诺的函数进行单元测试。我在验证是否存在挑战模拟函数被调用。这是我所做的。，

// codetotest.js
const { SomeModule, isSomething, isSomethingElse } = require("some-module");

exports.somefunction = (param1, param2)=> {
    const someModule = new SomeModule();

    someModule.someMethod("aaa", isSomething);
    someModule.someMethod("bbb", isSomethingElse);

    return (someModule.someOtherMethod(param1)
    .then(()=>{someModule.run(param2)}));
}

这是测试文件，测试表明未调用模拟函数，但我确实看到模拟函数中的控制台语句正在显示。

// codetotest.test.js
const { somefunction} = require("./codetotest.js");
const { SomeModule } = require("some-module");

jest.mock("some-module", () => {
    return {
        SomeModule: jest.fn().mockImplementation(() => {
            return {
                someMethod: jest.fn((param, fn) => { console.log("This prints!"); }),
                someOtherMethod: jest.fn((param) => { return Promise.resolve(() => { }) }),
                run: jest.fn((param) => { return Promise.resolve(() => { return []; }) })
            }
        })
    };
});

afterEach(() => {
    jest.resetAllMocks();
    jest.restoreAllMocks();
});

describe("Test codetotest.js", () => {
    it("somefunction() - success", async () => {
        const someModule = new SomeModule();

        let output = await somefunction("param1", "param2");

        expect(SomeModule).toHaveBeenCalled();
        expect(someModule.someMethod).toHaveBeenCalled(); // This fails

        await expect(someModule.someOtherMethod.mock.results[0]).resolves;
        expect(someModule.someOtherMethod).toHaveBeenCalled(); // This fails

        await expect(someModule.run.mocks.results[0]).resolves;
        expect(someModule.run).toHaveBeenCalled(); // This fails
    });
});

感谢任何帮助/指针。

谢谢。

P.S：在 nodeJs 开发和单元测试方面，我还是个初学者。

【问题讨论】：

标签： node.js unit-testing jestjs

【解决方案1】：

我在这上面花了很长时间，最后发现实例化的模拟类没有正确返回模拟的方法。 This 的回答提示了我哪里出错了。

因此，我不得不按如下方式更改我的测试文件。，

// codetotest.test.js
const { somefunction} = require("./codetotest.js");
const { SomeModule } = require("some-module");

jest.mock("some-module", function() {
    return {
        SomeModule: jest.fn().mockImplementation(function() { // Arrow function cannot be used as constructor
            // Because I was not using the 'this' operator, my constructor always returned empty
            this.someMethod = jest.fn((param, fn) => { console.log("This prints!"); });
            this.someOtherMethod = jest.fn((param) => { return Promise.resolve(() => { }) });
            this.run = jest.fn((param) => { return Promise.resolve(() => { return []; }) });
            return {
                someMethod: this,someMethod,
                someOtherMethod: this.someOtherMethod,
                run: this.run
            }
        })
    };
});

afterEach(() => {
    jest.restoreAllMocks();
});

describe("Test codetotest.js", () => {
    it("somefunction() - success", async () => {
        await somefunction("param1", "param2");

        expect(SomeModule).toHaveBeenCalled();
        expect(SomeModule.mock.instances[0].someMethod).toHaveBeenCalled(); // This works
        expect(SomeModule.mock.instances[0].someOtherMethod).toHaveBeenCalled(); // This works
        expect(someModule.mock.instances[0].run).toHaveBeenCalled(); // This works
    });
});

【讨论】：