mocha_expects_method.rb

#example.rb
class Example
	def initialize(method_name)
		send method_name
	end
end


#example_test.rb
require 'mocha'

must 'invoke method with given name' do
	obj.expects(:some_method_name).once	#once is optional, expecting only one invoke is a default behaviour for Mocha
	obj = Example.new(:some_method_name)
end

#The only thing you want to know is that method named #some_method_name will be invoked on obj.
#You don't need define this method for this.