Restore uniqueness scope values after verifying each scope.

A test for a validation with multiple scopes would always pass as long
as there was a validation with the first scope. Subsequent scopes would
pass verification because the first scope value had already been made
unique.

lib/shoulda/matchers/active_model/validate_uniqueness_of_matcher.rb

@@ -133,6 +133,8 @@ module Shoulda # :nodoc:
               @subject.send("#{scope}=", next_value)
 
               if allows_value_of(existing_value, @expected_message)
+                @subject.send("#{scope}=", previous_value)
+
                 @negative_failure_message <<
                   " (with different value of #{scope})"
                 true

spec/shoulda/active_model/validate_uniqueness_of_matcher_spec.rb

@@ -66,11 +66,12 @@ describe Shoulda::Matchers::ActiveModel::ValidateUniquenessOfMatcher do
     before do
       @model = define_model(:example, :attr   => :string,
                                       :scope1 => :integer,
-                                      :scope2 => :integer) do
-        attr_accessible :attr, :scope1, :scope2
+                                      :scope2 => :integer,
+                                      :other => :integer) do
+        attr_accessible :attr, :scope1, :scope2, :other
         validates_uniqueness_of :attr, :scope => [:scope1, :scope2]
       end.new
-      @existing = Example.create!(:attr => 'value', :scope1 => 1, :scope2 => 2)
+      @existing = Example.create!(:attr => 'value', :scope1 => 1, :scope2 => 2, :other => 3)
     end
 
     it "should pass when the correct scope is specified" do
@@ -81,10 +82,18 @@ describe Shoulda::Matchers::ActiveModel::ValidateUniquenessOfMatcher do
       @existing.should validate_uniqueness_of(:attr).scoped_to(:scope1, :scope2)
     end
 
-    it "should fail when a different scope is specified" do
+    it "should fail when too narrow of a scope is specified" do
+      @model.should_not validate_uniqueness_of(:attr).scoped_to(:scope1, :scope2, :other)
+    end
+
+    it "should fail when too broad of a scope is specified" do
       @model.should_not validate_uniqueness_of(:attr).scoped_to(:scope1)
     end
 
+    it "should fail when a different scope is specified" do
+      @model.should_not validate_uniqueness_of(:attr).scoped_to(:other)
+    end
+
     it "should fail when no scope is specified" do
       @model.should_not validate_uniqueness_of(:attr)
     end