Rspec Testing

require 'spec_helper'
require_relative '../my_example'

describe MyExample do

let(:message_var) {"A message"}

  context 'when creating' do

    it 'should call message method with message_var' do
      expect_any_instance_of(MyExample).to receive(:message).with(message_var)
      MyExample.new(message_var)
    end

    it 'should call message method with message_var and return message_var in reverse' do
      expect_any_instance_of(MyExample).to receive(:message).with(message_var).and_return("this should fail")
      MyExample.new(message_var)
    end
  end
end

../my_example

class MyExample

  def initialize(m)
    message(m)
  end

  def message(m)
    return m.reverse
  end
end