Added tests and fixed some existing ones.

lib/mongo_mapper/plugins/keys.rb

@@ -193,7 +193,7 @@ def attributes=(attrs)
 
         def attributes
           HashWithIndifferentAccess.new.tap do |attrs|
-            keys.select { |name,key| !self[key.name].nil? }.each_pair do |name, key|
+            keys.select { |name,key| !self[key.name].nil? || key.type == ObjectId }.each_pair do |name, key|
               value = key.set(self[key.name])
               attrs[name] = value
             end

test/unit/test_document.rb

@@ -204,5 +204,46 @@ class Post
         (@document.new('_id' => @oid) == another_document.new('_id' => @oid)).should be(false)
       end
     end
+
+    context "nil attributes" do
+
+      should "list all the keys and default non nil attributes" do
+       doc = @document.new
+       doc.keys.keys.sort.should == ['_id', 'age', 'name']
+       doc.attributes.keys.sort.should == ['_id']
+      end
+
+      should "list all the keys and non nil attributes" do
+       doc = @document.new(:name => "John")
+       doc.keys.keys.sort.should == ['_id', 'age', 'name']
+       doc.attributes.keys.sort.should == ['_id','name']
+      end
+
+      should "list all the keys and pickup changed nil attributes" do
+       doc = @document.new(:name => "John")
+       doc.keys.keys.sort.should == ['_id', 'age', 'name']
+       doc.attributes.keys.sort.should == ['_id','name']
+
+       doc.name = nil
+
+       doc.keys.keys.sort.should == ['_id', 'age', 'name']
+       doc.attributes.keys.sort.should == ['_id']
+      end
+
+      should "list all the keys and pickup changed nil and non-nil attributes" do
+       doc = @document.new(:name => "John")
+       doc.keys.keys.sort.should == ['_id', 'age', 'name']
+       doc.attributes.keys.sort.should == ['_id','name']
+
+       doc.name = nil
+       doc.age = 12
+
+       doc.keys.keys.sort.should == ['_id', 'age', 'name']
+       doc.attributes.keys.sort.should == ['_id','age']
+      end
+
+    end
+
   end # instance of a document
 end # DocumentTest
+

test/unit/test_embedded_document.rb

@@ -364,14 +364,16 @@ def passwd
       context "attributes" do
         should "default to hash with all keys" do
           doc = @document.new
-          doc.attributes.keys.sort.should == ['_id', 'age', 'name']
+          doc.keys.keys.sort.should == ['_id', 'age', 'name']
+          doc.attributes.keys.sort.should == ['_id']
         end
 
         should "return all keys with values" do
           doc = @document.new(:name => 'string', :age => nil)
-          doc.attributes.keys.sort.should == ['_id', 'age', 'name']
+          doc.attributes.keys.sort.should == ['_id', 'name']
+          doc.keys.keys.sort.should == ['_id', 'age', 'name']
           doc.attributes.values.should include('string')
-          doc.attributes.values.should include(nil)
+          #doc.attributes.values.should include(nil)
         end
 
         should "have indifferent access" do
@@ -384,14 +386,16 @@ def passwd
       context "to_mongo" do
         should "default to hash with _id key" do
           doc = @document.new
-          doc.to_mongo.keys.sort.should == ['_id', 'age', 'name']
+          doc.to_mongo.keys.sort.should == ['_id']
+          doc.keys.keys.sort.should == ['_id', 'age', 'name']
         end
 
         should "return all keys" do
           doc = @document.new(:name => 'string', :age => nil)
-          doc.to_mongo.keys.sort.should == ['_id', 'age', 'name']
+          doc.keys.keys.sort.should == ['_id', 'age', 'name']
+          doc.to_mongo.keys.sort.should == ['_id','name']
           doc.to_mongo.values.should include('string')
-          doc.to_mongo.values.should include(nil)
+          #doc.to_mongo.values.should include(nil)
         end
       end
 
@@ -675,3 +679,4 @@ def name_and_age=(new_value)
     end # instance of a embedded document
   end
 end
+