Feature: Spies

  Object Oriented Programming is all about messages sent between the objects.  If you follow principles like "Tell, Don't Ask", you will enable yourself to combine Bogus's powerful feature of faking objects with it's ability to verify object interactions.

  Typically, stubbing libraries force you to first stub a method, so that you can later make sure it was called. However, if you use fakes, Bogus lets you verify that a method was called (or not) without stubbing it first.

  Background:
    Given a file named "foo.rb" with:
    """ruby
    class Library
      def checkout(book)
        # marks book as checked out
      end
    end

    class Student
      def initialize(library)
        @library = library
      end

      def study(*book_titles)
        book_titles.each do |book_title|
          @library.checkout(book_title)
        end
      end
    end
    """

  Scenario: Ensuring methods were called
    Then spec file with following content should pass:
    """ruby
    describe Student do
      fake(:library)

      it "studies using books from library" do
        student = Student.new(library)

        student.study("Moby Dick", "Sherlock Holmes")

        library.should have_received.checkout("Moby Dick")
        library.should have_received.checkout("Sherlock Holmes")
      end
    end
    """

  Scenario: Spying on methods that do not exist
    Then spec file with following content should fail:
    """ruby
    describe Student do
      fake(:library)

      it "studies using books from library" do
        student = Student.new(library)

        student.study("Moby Dick")

        library.should_not have_received.return_book("Moby Dick")
      end
    end
    """

  Scenario: Spying on methods with wrong number of arguments
    Then spec file with following content should fail:
    """ruby
    describe Student do
      fake(:library)

      it "studies using books from library" do
        student = Student.new(library)

        student.study("Moby Dick", "Sherlock Holmes")

        library.should_not have_received.checkout("Moby Dick", 
          "Sherlock Holmes")
      end
    end
    """

  Scenario: Spying on previously stubbed methods
    Then spec file with following content should pass:
    """ruby
    describe Student do
      fake(:library)

      it "studies using books from library" do
        stub(library).checkout("Moby Dick") { "checked out" }

        library.checkout("Moby Dick").should == "checked out"

        library.should have_received.checkout("Moby Dick")
      end
    end
    """