nesting_prob_demo.rb

class TestLibrary
  @@stack = []
  def self.stack
    @@stack
  end
  
  def self.test_methods
    public_instance_methods.grep(/^test/)
  end

  def self.should(name, &block)
    method_name = "test_#{name.gsub(/\s/, '_')}"
    define_method(method_name, &block)
    
    (ancestors - [self]).each do |klass|
      klass.test_methods.each {|method| send(:undef_method, method)} unless klass > TestLibrary
    end
  end
end

module Kernel
  def context(name, &block)
    sklass = TestLibrary.stack.last || TestLibrary
    klass  = Class.new(sklass)
    sklass.const_set(name, klass)
    klass.stack << klass
    klass.class_eval(&block)
    klass.stack.pop
    klass
  end
end

context "A" do
  should("say hi bob") { true }

  context "B" do
    should("say hi sally") { true }
  end

  should("say hi ricky") { true }
end

p "Context A: #{TestLibrary::A.test_methods}"
p "Context B: #{TestLibrary::A::B.test_methods}"

# Output
#=> Context A: [:test_say_hi_bob, :test_say_hi_ricky]
#=> Context B: [:test_say_hi_sally, :test_say_hi_ricky]