Now with tests!

output

» ruby -wv test.rb                                                                     <~>
ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin11.2.0]
Run options: 

# Running tests:

..

Finished tests in 0.000647s, 3091.1901 tests/s, 3091.1901 assertions/s.

2 tests, 2 assertions, 0 failures, 0 errors, 0 skips

problems.rb

require 'test/unit'

class Problem
end

class Bitch < Problem
end

Problems = []
99.times { Problems << Problem.new }

class TestProblems < Test::Unit::TestCase
  def test_number_of_problems
    assert_equal 99, Problems.length
  end

  def test_problem_types
    assert_nil Problems.detect { |p| p.is_a?(Bitch) }
  end
end