Feature: Safe stubbing

  Most Ruby test double libraries let you stub methods that don't exist.  Bogus is different in this respect: not only does it not allow stubbing methods that don't exist, it also ensures that the number of arguments you pass to those methods matches the method definition.

  The stubbing syntax is:

      stub(object).method_name(arg1, arg2, ...) { return_value }

  Background:
    Given a file named "library.rb" with:
    """ruby
    class Library
      def checkout(book)
      end
    end
    """

  Scenario: Stubbing methods that exist on real object
    Then spec file with following content should pass:
    """ruby
    require_relative 'library'

    describe Library do
      it "does something" do
        library = Library.new
        stub(library).checkout("some book") { :checked_out }

        expect(library.checkout("some book")).to eq(:checked_out)
      end
    end
    """

  Scenario: Stubbing methods that do not exist on real object
    Then spec file with following content should fail:
    """ruby
    require_relative 'library'

    describe Library do
      it "does something" do
        library = Library.new
        stub(library).buy("some book") { :bought }
      end
    end
    """

  Scenario: Stubbing methods with wrong number of arguments
    Then spec file with following content should fail:
    """ruby
    require_relative 'library'

    describe Library do
      it "does something" do
        library = Library.new
        stub(library).checkout("some book", "another book") { :bought }
      end
    end
    """

  Scenario: Stubs allow the methods to be called
    Then spec file with following content should pass:
    """ruby
    require_relative 'library'

    describe Library do
      it "does something" do
        library = Library.new
        stub(library).checkout("some book") { :bought }
      end
    end
    """
 
  Scenario: Stubbing methods multiple times
    Then spec file with following content should fail:
    """ruby
    require_relative 'library'

    describe Library do
      it "stubbing with too many arguments" do
        library = Library.new

        stub(library).checkout("some book") { :bought }
        stub(library).checkout("book", "and one argument too many") { :whatever }
      end
    end
    """