addPositiveNumbers Jest tests

index.test.js

import { addPositiveNumbers } from '../index';
import * as IsPositiveNumber from "../isPositiveNumber";

IsPositiveNumber.isPositiveNumber = jest.fn();

describe('addPositiveNumbers', () => {
    afterEach(() => {
        jest.clearAllMocks();
    });

    test('Returns the correct answer', () => {
        IsPositiveNumber.isPositiveNumber.mockReturnValueOnce(true).mockReturnValueOnce(true);
        expect(addPositiveNumbers(1, 2)).toBe(3);
    });

    test('Throws when non-number passed', () => {
        IsPositiveNumber.isPositiveNumber.mockReturnValueOnce(false).mockReturnValueOnce(true);
        expect(() => {
            addPositiveNumbers('1', 3);
        }).toThrow('Parameter was not a number.');
    });

    test('Expect isPositiveNumber to have been called twice', () => {
        IsPositiveNumber.isPositiveNumber.mockReturnValueOnce(true).mockReturnValueOnce(true);
        expect(addPositiveNumbers(1, 2)).toBe(3);
        expect(IsPositiveNumber.isPositiveNumber).toHaveBeenCalled();
        expect(IsPositiveNumber.isPositiveNumber).toHaveBeenCalledTimes(2);
        expect(IsPositiveNumber.isPositiveNumber).toHaveBeenCalledWith(1);
        expect(IsPositiveNumber.isPositiveNumber).toHaveBeenCalledWith(2);
    });
});