[英]How to mock dependency classes for unit testing with mocha.js?
Given that I have two ES6 classes.鉴于我有两个 ES6 类。
This is class A:这是A类:
import B from 'B';
class A {
someFunction(){
var dependency = new B();
dependency.doSomething();
}
}
And class B: B类:
class B{
doSomething(){
// does something
}
}
I am unit testing using mocha (with babel for ES6), chai and sinon, which works really great.我正在使用 mocha(ES6 的 babel)、chai 和 sinon 进行单元测试,效果非常好。 But how can I provide a mock class for class B when testing class A?
但是,在测试 A 类时,如何为 B 类提供模拟类?
I want to mock the entire class B (or the needed function, doesn't actually matter) so that class A doesn't execute real code but I can provide testing functionality.我想模拟整个 B 类(或所需的功能,实际上并不重要),以便 A 类不执行真正的代码,但我可以提供测试功能。
This is, what the mocha test looks like for now:这就是 mocha 测试现在的样子:
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???
});
});
You can use SinonJS to create a stub to prevent the real function to be executed.您可以使用 SinonJS 创建一个存根来阻止真正的函数被执行。
For example, given class A:例如,给定 A 类:
import B from './b';
class A {
someFunction(){
var dependency = new B();
return dependency.doSomething();
}
}
export default A;
And class B: B类:
class B {
doSomething(){
return 'real';
}
}
export default B;
The test could look like: ( sinon < v3.0.0 )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:编辑:对于 sinon 版本 >= v3.0.0,使用这个:
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');
});
});
You can then restore the function if necessary using object.method.restore();
如有必要,您可以使用
object.method.restore();
恢复该函数object.method.restore();
: :
var stub = sinon.stub(object, "method");
var stub = sinon.stub(object, "method");
Replaces object.method with a stub function.用存根函数替换 object.method。 The original function can be restored by calling
object.method.restore();
可以通过调用
object.method.restore();
恢复原函数object.method.restore();
(orstub.restore();
).(或
stub.restore();
)。 An exception is thrown if the property is not already a function, to help avoid typos when stubbing methods.如果该属性还不是函数,则会引发异常,以帮助避免在存根方法时出现拼写错误。
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