Create a shared example for Numercial Submatchers.

* Verify that all submatchers respond to the necessary interface
* See: #357 for a reason why this is necessary

spec/shoulda/matchers/active_model/comparison_matcher_spec.rb

@@ -1,6 +1,10 @@
 require 'spec_helper'
 
 describe Shoulda::Matchers::ActiveModel::ComparisonMatcher do
+  it_behaves_like 'a numerical submatcher' do
+    subject {  Shoulda::Matchers::ActiveModel::ComparisonMatcher.new(0, :>) }
+  end
+
   context 'is_greater_than' do
     it { instance_with_validations(greater_than: 2).should matcher.is_greater_than(2) }
     it { instance_without_validations.should_not matcher.is_greater_than(2) }

spec/shoulda/matchers/active_model/odd_even_number_matcher_spec.rb

@@ -1,6 +1,10 @@
 require 'spec_helper'
 
 describe Shoulda::Matchers::ActiveModel::OddEvenNumberMatcher do
+  it_behaves_like 'a numerical submatcher' do
+    subject {  Shoulda::Matchers::ActiveModel::OddEvenNumberMatcher.new(:attr) }
+  end
+
   context 'given an attribute that only allows odd number values' do
     it 'matches' do
       validating_odd_number.should new_odd_matcher

spec/shoulda/matchers/active_model/only_integer_matcher_spec.rb

@@ -1,6 +1,10 @@
 require 'spec_helper'
 
 describe Shoulda::Matchers::ActiveModel::OnlyIntegerMatcher do
+  it_behaves_like 'a numerical submatcher' do
+    subject { Shoulda::Matchers::ActiveModel::OnlyIntegerMatcher.new(:attr) }
+  end
+
   context 'given an attribute that only allows integer values' do
     it 'matches' do
       validating_only_integer.should new_matcher

spec/support/shared_examples/numerical_submatcher_spec.rb

@@ -0,0 +1,15 @@
+require 'spec_helper'
+
+shared_examples 'a numerical submatcher' do
+  it 'implements the with_message method' do
+    subject.should respond_to(:with_message).with(1).arguments
+  end
+
+  it 'implements the allowed_types method' do
+    subject.should respond_to(:allowed_types).with(0).arguments
+  end
+
+  it 'implements the matches? method' do
+    subject.should respond_to(:matches?).with(1).arguments
+  end
+end