calculator_test.rb

class Calculator
  def sum(a, b)
    a + b
  end

  def product(a, b)
    a * b
  end
end

require 'test/unit'

class CalculatorTest < Test::Unit::TestCase
  def test_calculator_should_add_numbers_for_sum
    calculator = Calculator.new
    assert_equal 4, calculator.sum(2, 2)
  end

  def test_calculator_should_multiply_numbers_for_the_product
    calculator = Calculator.new
    assert_equal 10, calculator.product(2, 5)
  end
end