I'm writing a Jest test. I need to test a function that calls a function in another .js file. This called function returns a promise that resolves to a string. When I start the test I get the error "file.function is not a function", where instead of "file" I have the name of the imported js file and instead of "function" I have the name of the function that return the promise.
Below my test:
test('test', () => {
jest.mock('../file', () => {
function: jest.fn().mockReturnValue('Returned String')
});
myFunction();
expect().toBe();
});
Explanation: first of all I mocked the module which contains the function that return a promise. With second parameter (of jest.mock) I mocked the function contained in mocked module. Next I call the function that I want to test (this function will call mocked function). Finally, I test the expectations. Someone can help me, please. I don't know how I can resolve, thanks to all.
jest.mock should be at the same level as imports. If you need to test multiple cases just mock the returned/resolved value each time.
import { myFunction } from './fn';
import { function } from '../file';
jest.mock('../file', () => {
function: jest.fn(),
});
describe('myFunction tests', () => {
describe('With returned string', () => {
beforeEach(() => {
function.mockReturnValue('Returned String');
});
it('should do sth', () => {
myFunction();
// expect(...).toBe(...);
});
});
describe('With returned number', () => {
beforeEach(() => {
function.mockReturnValue(7);
});
it('should do other thing', () => {
myFunction();
// expect(...).toBe(...);
});
});
});