How can I mock this http request using jest? - node.js

Question

I am new to using Jest for unit tests. How can I mock this simple http request method "getData"? Here is the class:
const got = require("got")
class Checker {
constructor() {
this.url
this.logData = this.logData.bind(this);
this.getData = this.getData.bind(this);
}
async getData(url) {
const response = await got(url);
const data = await response.body;
return data;
}
async logData(first, second, threshold) {
let data = await this.getData(this.url)
console.log("received " + data.body);
}
}
I am trying to mock "getData" so I can write a unit test for "logData". Do I need to mock out the entire "got" module? Thanks.

Answer 1

If you change invoking got to got.get you should be able to have a working test like so:
const got = require('got');
const Checker = require('../index.js');
describe("some test", () => {
beforeEach(() => {
jest.spyOn(got, 'get').mockResolvedValue({ response: { body: { somekey: "somevalue" } } } );
});
it("works", async () => {
new Checker().getData();
expect(got.get).toBeCalledTimes(1);
})
})

Answer 2

One approach is to use dependency injection. Instead of calling 'got' directly, you can 'ask for it' in the class constructor and assign it to a private variable. Then, in the unit test, pass a mock version instead which will return what you want it to.
const got = require("got");
class Checker {
constructor(gotService) {
this.got = gotService;
this.logData = this.logData.bind(this);
this.getData = this.getData.bind(this);
}
async getData(url) {
const response = await this.got(url);
const data = await response.body;
return data;
}
async logData(first, second, threshold) {
let data = await this.getData(this.url)
console.log("received " + data.body);
}
}
//real code
const real = new Checker(got);
//unit testable code
const fakeGot = () => Promise.resolve(mockedData);
const fake = new Checker(fakeGot);
Here is what we are doing:
'Inject' got into the class.
In the class, call our injected version instead of directly calling the original version.
When it's time to unit test, pass a fake version which does what you want it to.

Answer 3

You can include this directly inside your test files. Then trigger the test that makes the Http request and this will be provided as the payload.
global.fetch = jest.fn(() =>
Promise.resolve({
json: () => Promise.resolve({ data: { eth: 0.6, btc: 0.02, ada: 1 } }),
})
);
it('should return correct mock token values', async () => {
const addresses = ["mockA", "mockB", "mockC"];
const res = await getTokenData(addresses);
expect(res.data).toEqual({ eth: 0.6, btc: 0.02, ada: 1 });
});