text: const sum = require('./sum')
  
  test('adds 1 + 2 to equal 3',() => {
      expect(sum(1, 2)).toBe(3)
  })
  
  test('adds 1 + null to equal 1',() => {
      expect(sum(1, null)).toBe(1)
  })
  
  test('adds null + 1 to equal 1',() => {
      expect(sum(null, 1)).toBe(1)
  })
  