Return an integer for fixnum columns for inclusion

* Fixes https://github.com/thoughtbot/shoulda-matchers/issues/179

NEWS.md

@@ -1,5 +1,8 @@
 # HEAD
 
+* Fix a bug in `ensure_inclusion_of` that would cause issues with using
+  `in_array` with an integer value.
+
 * Add support for PostgreSQL UUID columns to `validates_uniqueness_of` (#334).
 
 * Fix `validates_numericality_of` so that `is_equal_to` submatcher works

lib/shoulda/matchers/active_model/ensure_inclusion_of_matcher.rb

@@ -23,6 +23,7 @@ module Shoulda # :nodoc:
 
       class EnsureInclusionOfMatcher < ValidationMatcher # :nodoc:
         ARBITRARY_OUTSIDE_STRING = 'shouldamatchersteststring'
+        ARBITRARY_OUTSIDE_FIXNUM = 123456789
 
         def initialize(attribute)
           super(attribute)
@@ -144,8 +145,21 @@ module Shoulda # :nodoc:
         end
 
         def value_outside_of_array
-          if @array.include?(ARBITRARY_OUTSIDE_STRING)
+          if @array.include?(outside_value)
             raise CouldNotDetermineValueOutsideOfArray
+          else
+            outside_value
+          end
+        end
+
+        def outside_value
+          @outside_value ||= find_outside_value
+        end
+
+        def find_outside_value
+          case @subject.send(@attribute.to_s)
+          when Fixnum
+            ARBITRARY_OUTSIDE_FIXNUM
           else
             ARBITRARY_OUTSIDE_STRING
           end

spec/shoulda/matchers/active_model/ensure_inclusion_of_matcher_spec.rb

@@ -8,6 +8,16 @@ describe Shoulda::Matchers::ActiveModel::EnsureInclusionOfMatcher do
     end
   end
 
+  context 'with an integer column' do
+    it 'can verify a zero in the array' do
+      model = define_model(:example, :attr => :integer) do
+        validates_inclusion_of :attr, :in => [0, 1, 2]
+      end.new
+
+      model.should ensure_inclusion_of(:attr).in_array([0,1,2])
+    end
+  end
+
   context 'with true/false values' do
     it 'can verify outside values to ensure the negative case' do
       define_model(:example, :attr => :string).new.