Testing Async Code

Latte provides a simple way to test asynchronous code with async/await.

async-code.test.js

function fetchData() {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve('peanut butter');
        }, 1000);
    });
}

describe(`Async tests`, () => {
    it(`fetchData returns peanut butter`, async () => {
        const data = await fetchData();
        expect(data).toBe('peanut butter');
    })
})

toBeResolvedWith()

The toBeResolvedWith matcher is used to test that a promise resolves with a specific value. It takes the expected value as its argument.

async-code.test.js

function fetchData() {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve('peanut butter');
        }, 1000);
    });
}
describe(`Async tests`, () => {
    it(`fetchData returns peanut butter`, async () => {
        const data = await fetchData();
        expect(data).toBeResolvedWith('peanut butter');
    })
})