jest test function code example
Example 1: jest mock implementation
describe("mockImplementation", () => {
test("function", () => {
const mockFn1 = jest.fn().mockImplementation(() => 42);
const mockFn2 = jest.fn(() => 42);
expect(mockFn1()).toBe(42);
expect(mockFn2()).toBe(42);
});
Example 2: testing with jest
npm i jest --save -dev
-> In Package.json change the Script object(watchAll - jest will run auto)
"test" : "jest --watchAll"
-> test file should be named such way that re used by jest can recognize it
like filename.<test> or <spec> or skip it.js
Ex: sum.test.js or sum.spec.js or sum.js
-> require the target for testing file in this test file then enjoy testing.
-> visit jestWebsite-> Docs.
Example 3: write unit test jest first before json function
const axios = require('axios');
const Users = require('./users');
jest.mock('axios');
test('should fetch users', () => {
const users = [{
"id": 1,
"first_name": "Robert",
"last_name": "Schwartz",
"email": "[email protected]"
}, {
"id": 2,
"first_name": "Lucy",
"last_name": "Ballmer",
"email": "[email protected]"
}];
const resp = { data : users };
axios.get.mockImplementation(() => Promise.resolve(resp));
Users.all().then(resp => expect(resp.data).toEqual(users));
});