sinon stub a method that was executed in then call of promise - unit-testing

Question

describe("/test" , ()=> {
// separate class 2
class2 = {
// function that i wanna stub
hi: function () {
return "hi";
}
}
// separate class 1
class1 = {
// function that i have stubbed and tested
method1: function() {
return new Promise((resolve, reject) => {
resolve(num);
})
}
}
// method that i will execute
var parent= function (){
class1.method1().then(()=>{
class2.hi();
})
}
// the test
it("should stub hi method",()=>{
var hiTest = sinon.stub(class2, 'hi').resolves(5);
var method1Test = sinon.stub(class1 , 'method1').resolves(5);
// this start the execution of the promise with then call
parent();
// this works fine and test pass
expect(method1Test.calledOnce.should.be.true);
// this doesn't work although i executed the function
expect(hiTest.calledOnce.should.be.true);
})
})
what i wanna do is test the hi method correctly .. because when i test if the method is executed once or not
although i executed it in the then call of the promise it doesn't show that and it make the calledOnce test fail

Answer 1

The problem here is that you are testing the code as if it is synchronous, when it is not (as you are using Promise).
To be able to test this properly we need to be able to hook onto the promise chain that is started with parentcalling class1.method1.
We can do this by returning the promise that calling class1.method1 returns.
In terms of the test itself, we need to make sure Mocha doesnt end the test while we are waiting for the promises, so we use the done callback parameter to tell Mocha when we think the test is finished.
describe("/test", ()=> {
class2 = {
hi: function () {
return "hi";
}
}
class1 = {
method1: function() {
return new Promise((resolve, reject) => {
resolve(num);
})
}
}
var parent = function (){
return class1.method1().then(()=>{
class2.hi();
})
}
it("should stub hi method", (done)=> {
var hiTest = sinon.stub(class2, 'hi').returns(5);
var method1Test = sinon.stub(class1 , 'method1').resolves(5);
parent().then(() => {
expect(method1Test.calledOnce.should.be.true);
expect(hiTest.calledOnce.should.be.true);
done();
});
})
})