Jest - how to mock a class in jest - reactjs

Question

I've been trying to mock a test in jest through the methods that they have on their documentation. By mocking the whole class but I can't seem to get it to work properly.
https://jestjs.io/docs/en/es6-class-mocks
jest.mock('../../../../../src/SubscriptionOrder');
SubscriptionOrder.prototype.createChargebeeSubscription = jest.fn(() => 'response');
const test = new SubscriptionOrder(
'subscription',
[{}],
'errorMethods',
'customerMethods',
);
test.createChargebeeSubscription();
I'd expect this to mock the createChargebeeSubscription method and return the string response but it seems to be returning undeifined
Then this is the piece of code I'm trying to run a test for as well.
const subscriptionOrder = new SubscriptionOrder(
'subscription',
subscriptionRequest,
errorMethods,
customerMethods,
);
const response = await subscriptionOrder.createChargebeeSubscription(token);
this.setState({ successfulSubmit: response });
I want to update the state to the string response but getting undefined instead. so it appears I'm kinda mocking something but just not properly.

Answer 1

You can use spyOn as follows to do the mocking for you. I also recommend that you set up and tear down this spy once you are finished.
So here's a sample piece of code which will do what you want:
describe('createChargebeeSubscription() method behaviour', () => {
let createChargebeeSubscriptionSpy;
let testResponse;
beforeAll(() => {
// Lets create an instance of your class first
const subscriptionOrder = new SubscriptionOrder(
'subscription',
subscriptionRequest,
errorMethods,
customerMethods
);
// Now use a spy to mock the return value from your function
createChargebeeSubscriptionSpy = jest.spyOn(subscriptionOrder, 'createChargebeeSubscription').mockImplementation(() => {
return 'response';
});
// Finally invoke the method being tested
testResponse = subscriptionOrder.createChargebeeSubscription();
});
afterAll(() => {
// Restore the functionality (ie. disable the spy) of your method
createChargebeeSubscriptionSpy.mockRestore();
});
it('verifies that the expected response was returned', () => {
expect(testResponse).toBe('response');
});
});