> These days I'm having problems with improving the test cases.
> It's not a good idea to run all the tests after improve test for each
> function since it takes much time.
> As well I can't run tests individually without errors again and again.
> (File not found, undefined constant,  undefined variable)
> I cannot find that my tests are correct or not.

First of all the tests should run standalone as well as part of
testsuite. I see lot of tests fail in both modes, so maybe that's the
reason why it fails for you?

> Please suggest me some way to get rid of this problem.
> Its very helpful if you can give one example for fixing a failing test in
> PMA_DisplayResults_test.php

Fix the tests and code to work together :-).