Also, while building a hierarchy of test classes, you may think that it might be a good idea to invoke tearDown() from the setUp() method of your base test class ... just in case something was not cleared ... somehow.

And then, while writing a test class, extending the base class (preferably indirectly), call super.setUp() AT THE END of your setUp() method ...

Disclaimer: I didn't write it this way, I just had to debug it :)