Add documentation for strict validation testing

lib/shoulda/matchers/active_model.rb

@@ -29,8 +29,19 @@ module Matchers
     #     end
     #     it { should allow_value("(123) 456-7890").for(:phone_number) }
     #     it { should_not allow_mass_assignment_of(:password) }
+    #     it { should allow_value('Activated', 'Pending').for(:status).strict }
+    #     it { should_not allow_value('Amazing').for(:status).strict }
     #   end
     #
+    # These tests work with the following model:
+    #
+    # class User < ActiveRecord::Base
+    #   validates_presence_of :name
+    #   validates_presence_of :phone_number
+    #   validates_format_of :phone_number, :with => /\\(\\d{3}\\) \\d{3}\\-\\d{4}/
+    #   validates_inclusion_of :status, :in => %w(Activated Pending), :strict => true
+    #   attr_accessible :name, :phone_number
+    # end
     module ActiveModel
     end
   end

lib/shoulda/matchers/active_model/allow_value_matcher.rb

@@ -11,6 +11,9 @@ module ActiveModel # :nodoc:
       # * <tt>with_message</tt> - value the test expects to find in
       #   <tt>errors.on(:attribute)</tt>. Regexp or string. If omitted,
       #   the test looks for any errors in <tt>errors.on(:attribute)</tt>.
+      # * <tt>strict</tt> - expects the model to raise an exception when the
+      #   validation fails rather than adding to the errors collection. Used for
+      #   testing `validates!` and the `:strict => true` validation options.
       #
       # Example:
       #   it { should_not allow_value('bad').for(:isbn) }