better mocked values

lib/fog/aws.rb

@@ -24,5 +24,49 @@ module Fog
       Fog::AWS::S3.reload
     end
 
+    if Fog.mocking?
+      srand(Time.now.to_i)
+
+      class Mock
+
+        def self.letters(length)
+          random_selection(
+            'abcdefghijklmnopqrstuvwxyz',
+            length
+          )
+        end
+
+        def self.numbers(length)
+          random_selection(
+            '0123456789',
+            length
+          )
+        end
+
+        def self.hex(length)
+          random_selection(
+            '0123456789abcdef',
+            length
+          )
+        end
+
+        def self.etag
+          hex(32)
+        end
+
+        private
+
+        def self.random_selection(characters, length)
+          selection = ''
+          length.times do
+            position = rand(characters.length)
+            selection << characters[position..position]
+          end
+          selection
+        end
+
+      end
+    end
+
   end
 end

lib/fog/aws/requests/s3/put_object.rb

@@ -56,7 +56,7 @@ else
             bucket = @data['Buckets'].select {|bucket| bucket['Name'] == bucket_name}.first
             bucket['Contents'] << {
               :body           => file[:body],
-              'ETag'          => Digest::SHA1.hexdigest(rand.to_s)[0...32],
+              'ETag'          => Fog::AWS::Mock.etag,
               'Key'           => object_name,
               'LastModified'  => Time.now.utc.strftime("%a, %d %b %Y %H:%M:%S +0000"),
               'Owner'         => { 'DisplayName' => 'owner', 'ID' => 'some_id'},