How can I mock this http request using jest?

user_12398673 0
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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.

jestjs node.js asynchronous mocking unit-testing
3 Answers

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);
    })
})
user_3606740

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:

  1. 'Inject' got into the class.
  2. In the class, call our injected version instead of directly calling the original version.
  3. When it's time to unit test, pass a fake version which does what you want it to.
user_160877700

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 });
});
user_34845570
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