fix for superfluous Rollback exception on failed validation

lib/mongo_record/active_record/connection_adapters.rb

@@ -85,7 +85,10 @@ def supports_count_distinct?
       # Transactions are not yet supported by Mongo, so this method simply
       # yields to the given block.
       def transaction(start_db_transaction=true)
-        yield
+        begin
+          yield
+        rescue ActiveRecord::Rollback
+        end
       end
 
       # Enable the query cache within the block. Ignored.

test/models/user.rb

@@ -1,3 +1,4 @@
 class User < ActiveRecord::Base
+  validates_presence_of :name
 end
 

test/mongo_record_test.rb

@@ -251,4 +251,22 @@ def test_update
     assert_equal "bar", v.name
   end
 
+  def test_validation
+    assert_equal 1, User.count
+
+    u = User.new
+    u.name = "foobar"
+    u.save
+    assert u.errors.empty?
+
+    assert_equal 2, User.count
+
+    u = User.new
+    u.password = "foobar"
+    u.save
+    assert !u.errors.empty?
+
+    assert_equal 2, User.count
+  end
+
 end