Directly return from authentication

Returns either true or an AuthenticationError if 
authentication wasn't successful.

This way you won't have to use callbacks on it so 
it is more in the spirit of Synchrony.

lib/em-synchrony/em-mongo.rb

@@ -9,7 +9,6 @@ module Mongo
 
     class Database
       def authenticate(username, password)
-        response = RequestResponse.new
         auth_result = self.collection(SYSTEM_COMMAND_COLLECTION).first({'getnonce' => 1})
 
         auth                 = BSON::OrderedHash.new
@@ -20,11 +19,10 @@ def authenticate(username, password)
 
         auth_result2 = self.collection(SYSTEM_COMMAND_COLLECTION).first(auth)
         if EM::Mongo::Support.ok?(auth_result2)
-          response.succeed true
+          true
         else
-          response.fail auth_result2
+          raise AuthenticationError, auth_result2["errmsg"]
         end
-        response
       end
     end
 

spec/em-mongo_spec.rb

@@ -231,20 +231,29 @@
     end
   end
 
-  it "authenticates" do
-    # For this to actually assert anything we will need to add the test user to
-    # the database
-    #
-    # From the Mongo shell:
-    # > use db
-    # > db.addUser('test', 'test')
-    EventMachine.synchrony do
-      database = EM::Mongo::Connection.new.db('db')
-      database.add_user('test', 'test')
-      auth = database.authenticate('test', 'test').callback do |cb|
-        cb.should == true
+  context "authentication" do
+    # these specs only get asserted if you run mongod with the --auth flag
+    it "successfully authenticates" do
+      # For this spec you will need to add this user to the database
+      #
+      # From the Mongo shell:
+      # > use db
+      # > db.addUser('test', 'test')
+      EventMachine.synchrony do
+        database = EM::Mongo::Connection.new.db('db')
+        database.authenticate('test', 'test').should == true
+        EventMachine.stop
+      end
+    end
+
+    it "raises an AuthenticationError if it cannot authenticate" do
+      EventMachine.synchrony do
+        database = EM::Mongo::Connection.new.db('db')
+        proc {
+          database.authenticate('test', 'wrong_password')
+        }.should raise_error(EventMachine::Mongo::AuthenticationError, "auth fails")
+        EventMachine.stop
       end
-      EventMachine.stop
     end
   end
 end