完善mock和测试

git-svn-id: http://code.alibabatech.com/svn/druid/trunk@830 b9813039-fb51-4c41-a8b9-e21c2acb5095

src/main/java/com/alibaba/druid/mock/MockStatement.java

@@ -57,13 +57,30 @@ public class MockStatement implements Statement {
         this.connection = fakeConnection;
     }
 
+    @SuppressWarnings("unchecked")
     @Override
     public <T> T unwrap(Class<T> iface) throws SQLException {
+        if (iface == null) {
+            return null;
+        }
+
+        if (iface.isInstance(this)) {
+            return (T) this;
+        }
+
         return null;
     }
 
     @Override
     public boolean isWrapperFor(Class<?> iface) throws SQLException {
+        if (iface == null) {
+            return false;
+        }
+
+        if (iface.isInstance(this)) {
+            return true;
+        }
+
         return false;
     }