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

Question

我正在尝试对返回承诺的函数进行单元测试。我在验证模拟函数是否被调用时遇到了挑战。这就是我所做的。

// 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，测试表明没有调用模拟函数，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/指示。

谢谢。

PS：对于nodeJs开发和单元测试，我还是一个初学者。

Answer 1

我花了相当多的时间在这上面，最后发现实例化的模拟类没有正确返回模拟方法。这个答案给了我一个提示，告诉我哪里出了问题。

因此，我必须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
    });
});