const calculator = require('./calculator')

describe('add', () => {
  test('adds 0 and 0', () => {
    expect(calculator.add(0, 0)).toBe(0)
  })

  test('adds 2 and 2', () => {
    expect(calculator.add(2, 2)).toBe(4)
  })

  test('adds positive numbers', () => {
    expect(calculator.add(2, 6)).toBe(8)
  })
})

describe('subtract', () => {
  test('subtracts numbers', () => {
    expect(calculator.subtract(10, 4)).toBe(6)
  })
})

describe('sum', () => {
  test('computes the sum of an empty array', () => {
    expect(calculator.sum([])).toBe(0)
  })

  test('computes the sum of an array of one number', () => {
    expect(calculator.sum([7])).toBe(7)
  })

  test('computes the sum of an array of two numbers', () => {
    expect(calculator.sum([7, 11])).toBe(18)
  })

  test('computes the sum of an array of many numbers', () => {
    expect(calculator.sum([1, 3, 5, 7, 9])).toBe(25)
  })
})

describe('multiply', () => {
  test('multiplies two numbers', () => {
    expect(calculator.multiply(2, 4)).toBe(8)
  })

  test('multiplies several numbers', () => {
    expect(calculator.multiply(2, 4, 6, 8, 10, 12, 14)).toBe(645120)
  })
})

describe('power', () => {
  test('raises one number to the power of another number', () => {
    expect(calculator.power(4, 3)).toBe(64) // 4 to third power is 64
  })
})

describe('factorial', () => {
  test('computes the factorial of 0', () => {
    expect(calculator.factorial(0)).toBe(1) // 0! = 1
  })

  test('computes the factorial of 1', () => {
    expect(calculator.factorial(1)).toBe(1)
  })

  test('computes the factorial of 2', () => {
    expect(calculator.factorial(2)).toBe(2)
  })

  test('computes the factorial of 5', () => {
    expect(calculator.factorial(5)).toBe(120)
  })

  test('computes the factorial of 10', () => {
    expect(calculator.factorial(10)).toBe(3628800)
  })
})