Ruby Testing with Minitest

# calculator.rb
class Calculator
  def add(a, b)
    a + b
  end

  def divide(a, b)
    raise ArgumentError, "Cannot divide by zero" if b == 0
    a.to_f / b
  end
end

# test_calculator.rb
require "minitest/autorun"
require_relative "calculator"

class CalculatorTest < Minitest::Test
  def setup
    @calc = Calculator.new
  end

  def test_add
    assert_equal 5, @calc.add(2, 3)
    assert_equal 0, @calc.add(-1, 1)
  end

  def test_divide
    assert_equal 2.5, @calc.divide(5, 2)
  end

  def test_divide_by_zero
    assert_raises(ArgumentError) { @calc.divide(1, 0) }
  end
end

assert_equal expected, actual        # ==
assert_nil value                     # value.nil?
assert_empty collection              # collection.empty?
assert_includes collection, item     # collection.include?(item)
assert_in_delta 3.14, calc.pi, 0.01 # approximate float comparison
assert_raises(SomeError) { ... }     # block must raise the error

def test_fizzbuzz
  assert_equal "FizzBuzz", fizzbuzz(15)
  assert_equal "Fizz", fizzbuzz(3)
  assert_equal "Buzz", fizzbuzz(5)
  assert_equal "7", fizzbuzz(7)
end

def fizzbuzz(n)
  return "FizzBuzz" if (n % 15).zero?
  return "Fizz" if (n % 3).zero?
  return "Buzz" if (n % 5).zero?
  n.to_s
end