Issue while running webdriver testcases in parallel using testng

[Vasuki]

Friends,

Without extending TestCase, the webdriver test cases are running fine in sequential order. If I run the testcases in parallel using testng (without extending TestCase), received the below exception.

org.testng.TestNGException:
Failure in JUnit mode for class com.**.TestCase: could not create/run JUnit test suite:
Cannot find JUnit method class junit.framework.TestSuite$1.warning

If I run the test case by extending TestCase, it is working fine (Eg: public class ActiveTestCase extends TestCase).

Please let me know how to run the test cases in parallel without extending TestCase.

Thanks