batch_size is taken into account when limit is 0/not set

lib/mongo/cursor.rb

@@ -220,12 +220,13 @@ module Mongo
     #   the server will determine the batch size.
     #
     # @return [Cursor]
-    def batch_size(size=0)
+    def batch_size(size=nil)
+      return @batch_size unless size
       check_modifiable
       if size < 0 || size == 1
         raise ArgumentError, "Invalid value for batch_size #{size}; must be 0 or > 1."
       else
-        @batch_size = size > @limit ? @limit : size
+        @batch_size = @limit != 0 && size > @limit ? @limit : size
       end
 
       self

test/unit/cursor_test.rb

@@ -76,6 +76,24 @@ class CursorTest < Test::Unit::TestCase
     should "cache full collection name" do
       assert_equal "testing.items", @cursor.full_collection_name
     end
+    
+    should "raise error when batch_size is 1" do
+      e = assert_raise ArgumentError do
+        @cursor.batch_size(1)
+        end
+        assert_equal "Invalid value for batch_size 1; must be 0 or > 1.", e.message
+    end
+    
+    should "use the limit for batch size when it's smaller than the specified batch_size" do
+      @cursor.limit(99)
+      @cursor.batch_size(100)
+      assert_equal 99, @cursor.batch_size
+      end
+      
+    should "use the specified batch_size" do
+      @cursor.batch_size(100)
+      assert_equal 100, @cursor.batch_size
+    end
   end
 
   context "Query fields" do