sum.spec.js

const sum = require('./sum');

describe('sum()', () => {
  it('should return 5 when arg a is 2 and arg b is 3', () => {
    expect(sum(2, 3)).toBe(5);
  });
  
  it('should return 1 when arg a is 1 and arg b is 0', () => {
    expect(sum(1, 0)).toBe(1);
  });
  
  it('should return 3 when arg a is 2 and arg b is 1', () => {
    expect(sum(2, 1)).toBe(3);
  });
});