Test Recursion, grossly

heart.rb

# code under test, you'll need to know their method name. 
# I've made two here to show the tests passing and failing

class Heart
  def self.some_recursive_method(num)
    if num > 0
      Heart.some_recursive_method(num - 1)
    end
  end

  def self.some_non_recursive_method(num)
    3 + 4 # whatevs
  end
end

recursion_test.rb

require 'minitest/autorun'
require_relative './heart'

class RecursionTest < Minitest::Test
  @@recursive_calls = 0

  class << Heart
    alias :old_some_recursive_method :some_recursive_method
    def some_recursive_method(num)
      # Check out cool other info in `caller`
      if !caller.first.match(/^#{__FILE__}/)
        @@recursive_calls += 1
      end
      old_some_recursive_method(num)
    end

    alias :old_some_non_recursive_method :some_non_recursive_method
    def some_non_recursive_method(num)
      if !caller.first.match(/^#{__FILE__}/)
        @@recursive_calls += 1
      end
      old_some_non_recursive_method(num)
    end
  end

  def test_recursion_happened
    @@recursive_calls = 0
    Heart.some_recursive_method(3)
    assert @@recursive_calls > 0
  end

  def test_that_should_fail_since_recursion_doesnt_happen
    @@recursive_calls = 0
    Heart.some_non_recursive_method(3)
    assert @@recursive_calls > 0
  end
end