Solving problem with internal classes

This is my fix, first commit will introduce a test to reproduce the error, the second one will be the fix for it.

Related to #59
This error handling code is a duplication in these 3 tests. Instead I propose to do what PHPUnit does:

1. in `xTest::run` create that error handler
2. when you catch an error, then throw an exception
3. that will be catched by try/catch block of test processing code and if test isn't expecting any exception to be thrown, then it will fail the test

Then you can remove code, that checks for errors, since on error test will fail automatically.