Change jest mock on class for single test - node.js

Question

I have an issue where I want to change what a class method returns for a single test while testing a different module. I have the following:
testingModule.test.js
const { testingModuleMethod } = require('../testingModule')
jest.mock('../helperClass', () =>
jest.fn().mockImplementation(() => ({
helperClassMethod: jest.fn()
}))
);
describe('testingModule.js', () => {
describe('testingModuleMethod', () => {
describe('when errors', () => {
const consoleSpy = jest.spyOn(console, 'error');
// SOMETHING NEEDS TO GO HERE TO CHANGE THE jest.mock ON LINE 3
await expect(testingModuleMethod(data)).rejects.toThrow('Error');
expect(consoleSpy).toHaveBeenCalled();
consoleSpy.mockRestore();
});
});
});
testingModule.js
const HelperClass = require('./helperClass');
const testingModuleMethod = async (data, callback) => {
try {
const objectToEvaluate = data.object;
const helperClassInstance = new HelperClass();
await helperClassInstance.helperClassMethod(objectToEvaluate);
log('info', "Success!");
callback(null, {});
} catch(error) {
log('error', 'Something went wrong')
}
};
No matter what I put in there I either get an error with the code (undefined) or it just ignores it and resolves due to the mock at the start. I have tried adding a spy as well as importing the class and using the prototype override.
I'm using node and "jest": "^27.0.6"

Answer 1

I have managed to answer this by doing the following:
Firstly I discovered that to mock a class like that I have to add a jest function into the mock like so:
describe('testingModuleMethod', () => {
describe('when errors', () => {
const consoleSpy = jest.spyOn(console, 'error');
HelperClass.mockImplementation(() => ({
helperClassMethod: jest.fn(() => { throw new Error('Error') })
}));
await expect(testingModuleMethod(data)).rejects.toThrow('Error');
expect(consoleSpy).toHaveBeenCalled();
consoleSpy.mockRestore();
});
});
This also had a knock on effect to the rest of the tests though so I added a beforeEach at the start that looks like:
HelperClass.mockImplementation(
jest.fn().mockImplementation(() => ({
helperClassMethod: jest.fn()
}))
);
Finally I needed to require the class. The overall test looks like this now and works:
const { testingModuleMethod } = require('../testingModule');
const HelperClass = require('./helperClass');
jest.mock('../helperClass', () =>
jest.fn().mockImplementation(() => ({
helperClassMethod: jest.fn()
}))
);
describe('testingModule.js', () => {
beforeEach(() => {
HelperClass.mockImplementation(
jest.fn().mockImplementation(() => ({
helperClassMethod: jest.fn()
}))
);
});
describe('testingModuleMethod', () => {
describe('when errors', () => {
const consoleSpy = jest.spyOn(console, 'error');
HelperClass.mockImplementation(() => ({
helperClassMethod: jest.fn(() => { throw new Error('Error') })
}));
await expect(testingModuleMethod(data)).rejects.toThrow('Error');
expect(consoleSpy).toHaveBeenCalled();
consoleSpy.mockRestore();
});
});
});