使用 mocha 和 chai 进行单元测试 async/await javascript

Question

Hey guys so I am currently working on this async function and writing unit test for this but it is not working it says AssertionError: expected undefined to equal 'Everytime I think of coding, I am happy' this is my code for the function:

async function funcFour() {// async automatically returns a promise
let result = new Promise((resolve) => {// returns a new promise named result
    setTimeout(() => {
        resolve(`Everytime I think of coding, I am happy`);//resolve happens after three seconds
    }, 1500)
});
const response = await result;//closing resolve of new promise
console.log(response);//console.logging response of new promise

} funcFour();

And here is my unit test for it:

describe("flirtFour()", () => {
it("Should return Everytime I think of coding, I am happy", async function () {
    return flirtFour().then(result => {
        expect(result).to.equal("Everytime I think of coding, I am happy")

    })
    

})

})

This is the first time I write unit test and I am trying to do it with async func so I am new to it. I really want to see how this is done so Thanks in advance:)

Answer 1

Although you have given funcFour() above and trying to test flirtFour() below, I am assuming they are the same. Now flirtFour() doesn't return anything as of now. You need to return the response from that function. By default, the returned value is undefined . Also remember that whatever you return from the async function gets wrapped into a Promise itself. So you're actually returning a Promise like so:-

return Promise.resolve(undefined) .

If you simply return response that will automatically be treated as

return Promise.resolve(response)

which is probably what you need.

So change your funcFour() to the following:-

async function funcFour() {// async automatically returns a promise
let result = new Promise((resolve) => {// returns a new promise named result
    setTimeout(() => {
        resolve(`Everytime I think of coding, I am happy`);//resolve happens after three seconds
    }, 1500)
});
const response = await result;
return response;
}