Quoting test for null value and string column

lib/Cake/Test/Case/Model/Datasource/Database/SqlserverTest.php

@@ -311,6 +311,10 @@ class SqlserverTest extends CakeTestCase {
 		$expected = "''";
 		$result = $this->db->value('', 'binary');
 		$this->assertSame($expected, $result);
+		
+		$expected = 'NULL';
+		$result = $this->db->value(null, 'string');
+		$this->assertSame($expected, $result);
 	}
 
 /**