Node.js 如何使用 mocha.js 模拟用于单元测试的依赖类

发布于09月21日

考虑到我有两门ES6课程.

这是A级:

import B from 'B';

class A {
    someFunction(){
        var dependency = new B();
        dependency.doSomething();
    }
}

B类:

class B{
    doSomething(){
        // does something
    }
}

我正在使用mocha(用于ES6的babel)、chai和sinon进行单元测试，这非常有效.但是，在测试类a时，如何为类B提供模拟类呢？

我想模拟整个B类(或者所需的函数，实际上并不重要)，这样A类就不会执行真正的代码，但我可以提供测试功能.

这就是目前的摩卡测试:

var A = require('path/to/A.js');

describe("Class A", () => {

    var InstanceOfA;

    beforeEach(() => {
        InstanceOfA = new A();
    });

    it('should call B', () => {
        InstanceOfA.someFunction();
        // How to test A.someFunction() without relying on B???
    });
});

推荐答案

您可以使用SinonJS创建一个stub，以防止执行真正的函数.

例如，给定A类:

import B from './b';

class A {
    someFunction(){
        var dependency = new B();
        return dependency.doSomething();
    }
}

export default A;

B类:

class B {
    doSomething(){
        return 'real';
    }
}

export default B;

这个测试可能看起来像:(sinon < v3.0.0)

describe("Class A", () => {

    var InstanceOfA;

    beforeEach(() => {
        InstanceOfA = new A();
    });

    it('should call B', () => {
        sinon.stub(B.prototype, 'doSomething', () => 'mock');
        let res = InstanceOfA.someFunction();

        sinon.assert.calledOnce(B.prototype.doSomething);
        res.should.equal('mock');
    });
});

EDIT: for sinon versions >= v3.0.0, use this:

describe("Class A", () => {

    var InstanceOfA;

    beforeEach(() => {
        InstanceOfA = new A();
    });

    it('should call B', () => {
        sinon.stub(B.prototype, 'doSomething').callsFake(() => 'mock');
        let res = InstanceOfA.someFunction();

        sinon.assert.calledOnce(B.prototype.doSomething);
        res.should.equal('mock');
    });
});

然后，如有必要，您可以使用object.method.restore();:

var stub = sinon.stub(object, "method");
Replaces object.method with a stub function. The original function can be restored by calling object.method.restore(); (or stub.restore();). An exception is thrown if the property is not already a function, to help avoid typos when stubbing methods.