a quick and dirty example of how to stub a method on an object

a simple method stubbing example.rb

require 'singleton'

class BlockTest
	def test
		puts "this is the real method."
		yield if block_given?
	end
end

class Object
	def stub_method(method)
		Foo::Bar.instance.stub_it(self, method)
	end
end

module Foo
	class Bar
		include Singleton
		
		def stub_it(object, method)
			object.instance_eval(<<-EOF, __FILE__, __LINE__)
		        def #{method}
		        	puts "this is a stubbed method."
	        		yield if block_given?
	        	end
	    	EOF
		end
	end
end

bt = BlockTest.new
bt.test { puts "and a block from the real method"}

bt.stub_method(:test)
bt.test { puts "and a block from the subbed method"}

# output is:
# => this is the real method.
# => and a block from the real method
# => this is a stubbed method.
# => and a block from the stubbed method