Fixed two specs.

spec/unit/checksumed_spec.rb

@@ -2,23 +2,21 @@
 require 'models/url'
 
 describe DataMapper::Is::Checksumed do
-  describe "Checksumed[]" do
-    subject { DataMapper::Is::Checksumed }
+  subject { Url }
+  before(:all) { subject.auto_migrate! }
 
+  describe "checksum" do
     let(:expected) { '2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824' }
 
     it "should calculate SHA256 checksums" do
-      subject.checksum('hello').should == expected
+      DataMapper::Is::Checksumed.checksum('hello').should == expected
     end
 
     it "should convert non-Strings to Strings" do
-      subject.checksum(:hello).should == expected
+      DataMapper::Is::Checksumed.checksum(:hello).should == expected
     end
   end
 
-  subject { Url }
-  before(:all) { subject.auto_migrate! }
-
   it "should record which properties are checksumed" do
     subject.checksumed_properties.should include(:url)
   end