async node js jest unit tests - node.js

Question

This is my nodejs code and I want to unit tests using jest and mocking the request function.
I am new to nodeJS, attached the mock function and the unit tests as well.
Please can someone add the right jest unit test code for below function.
async function getSomeTask(res) {
request.get({ url: someTaskUrl }, (response, body) => {
if (response.statusCode === 200) {
res.writeHead(200, { 'content-type': 'application/json' });
res.write(body);
res.end();
return;
}
const errorMessage = 'Failed';
res.status(400).json({ error: errorMessage });
});
}
// mock function in __mocks__
function get({url}) {
return this;
}
const handler = require("../../handler");
const request = require("../__mocks__/request");
jest.mock("request");
describe("testHandler", () => {
it("test", async () => {
const response1 = {
statusCode: 200,
body: { Test: "test" },
};
const url = "http://example.com";
jest.fn().mockImplementation({ url }, (response, body) => {
return Promise.resolve(response1);
});
const req = {
body: { requestId: 1111 },
capabilitiesCheckUrl: "http://capabilities-test",
};
const res = {};
const resp = handler.getSomeTask(res);
console.log(resp);
});
});
If possible give me an explanation as well.

Answer 1

You don't need to mock the entire request module by using jest.mock('request') and creating mocks inside __mocks__ directory. You can use jest.spyOn(request, 'get') to only mock request.get method.
handler.js:
const request = require('request');
const someTaskUrl = 'http://localhost:3000/api'
async function getSomeTask(res) {
request.get({ url: someTaskUrl }, (response, body) => {
if (response.statusCode === 200) {
res.writeHead(200, { 'content-type': 'application/json' });
res.write(body);
res.end();
return;
}
const errorMessage = 'Failed';
res.status(400).json({ error: errorMessage });
});
}
module.exports = {
getSomeTask,
};
handler.test.js:
const handler = require('./handler');
const request = require('request');
describe('73754637', () => {
test('should get some task success', () => {
jest.spyOn(request, 'get').mockImplementation((options, callback) => {
const mResponse = { statusCode: 200 };
const mBody = { Test: 'test' };
callback(mResponse, mBody);
});
const mRes = {
writeHead: jest.fn(),
write: jest.fn(),
end: jest.fn(),
};
handler.getSomeTask(mRes);
expect(request.get).toBeCalledWith({ url: 'http://localhost:3000/api' }, expect.any(Function));
expect(mRes.writeHead).toBeCalledWith(200, { 'content-type': 'application/json' });
expect(mRes.write).toBeCalledWith({ Test: 'test' });
expect(mRes.end).toBeCalledTimes(1);
});
});
Test result:
PASS stackoverflow/73754637/handler.test.js (10.283 s)
73754637
✓ should get some task success (5 ms)
------------|---------|----------|---------|---------|-------------------
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
------------|---------|----------|---------|---------|-------------------
All files | 81.82 | 50 | 100 | 81.82 |
handler.js | 81.82 | 50 | 100 | 81.82 | 12-13
------------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests: 1 passed, 1 total
Snapshots: 0 total
Time: 10.807 s, estimated 11 s