class Assertion < RunnableBlock
    def self.pass() [:pass]; end
    def self.fail(message) [:fail, message]; end
    def self.error(e) [:error, e]; end
    def run(situation)
      #apply expectation block
      @expectings << situation.evaluate(&@expectation_block) if @expectation_block
      action = @@assertions[@action]
      process_macro(situation,action[0]) { |actual| action[1].call(actual,*@expectings) }
    end

    @@assertions = Hash.new([false,Proc.new { |actual| actual ? Assertion.pass : Assertion.fail("failed") }])
    def self.assertion(name, expect_exception=false, &assertion_block)
      @@assertions[name] = [expect_exception,assertion_block]
      class_eval <<-END_RUBY
        def #{name}(*expectings,&expectation_block)
          @action, @expectings, @expectation_block = :#{name}, expectings, expectation_block
          self
        end
        END_RUBY
    end

    private
    def process_macro(situation, expect_exception)
      actual = situation.evaluate(&@definition)
      yield(expect_exception ? nil : actual)
    rescue Exception => e
      expect_exception ? yield(e) : Assertion.error(e)
    end
  end # Assertion