Changed matchers and added a lib/shoulda/matchers include so that matchers can be used outside shoulda

lib/shoulda/active_record/matchers.rb

@@ -1,2 +1,3 @@
+require 'shoulda/active_record/helpers'
 require 'shoulda/active_record/matchers/attribute_matcher'
 require 'shoulda/active_record/matchers/association_matcher'

lib/shoulda/active_record/matchers/attribute_matcher.rb

@@ -22,7 +22,10 @@ module Shoulda # :nodoc:
 
         def matches?(instance)
           @instance = instance
-          @expected_message ||= default_error_message(:invalid)
+          @expected_message ||= :invalid
+          if Symbol === @expected_message
+            @expected_message = default_error_message(@expected_message)
+          end
           @instance.send("#{@attribute}=", @value)
           !errors_match?
         end
@@ -35,6 +38,17 @@ module Shoulda # :nodoc:
           "Expected #{expectation}, got errors: #{pretty_error_messages(@instance)}"
         end
 
+        def description
+          if @value.nil?
+            "allow #{@attribute} to be blank"
+          else
+            description = "have an attribute called #{@attribute}"
+            description << " accepting value #{@value.inspect}"
+            description << " without error #{@expected_message.inspect}"
+            description
+          end
+        end
+
         private
 
         def errors_match?
@@ -77,7 +91,7 @@ module Shoulda # :nodoc:
       end
 
       def allow_blank_for(attr)
-        AttributeMatcher.new.for(attr).accepting_value(nil)
+        AttributeMatcher.new.for(attr).accepting_value(nil).with_message(:blank)
       end
     end
   end

lib/shoulda/matchers.rb

@@ -0,0 +1,9 @@
+require 'shoulda/active_record/matchers'
+
+module Thoughtbot
+  module Shoulda
+    module Matchers # :nodoc:
+      include ThoughtBot::Shoulda::ActiveRecord::Matchers
+    end
+  end
+end

test/other/active_record_matchers_test.rb

@@ -21,6 +21,16 @@ class ActiveRecordMatchersTest < Test::Unit::TestCase # :nodoc:
     end
   end
 
+  context "allow_blank_for(attr)" do
+    should "accept an attribute that allows a blank" do
+      assert_accepts allow_blank_for(:name), User.new
+    end
+
+    should "reject an attribute that doesn't allow a blank" do
+      assert_rejects allow_blank_for(:title), Product.new
+    end
+  end
+
   context "accept_value(value).for" do
     should "accept a good attribute value" do
       assert_accepts accept_value("good@example.com").for(:email), User.new