Test for cancellation was added
Implemented test cancellation

The cancellation mechanism for thread was implemented. The methods
Thread::cancel() and Thread::testcancel() where implemented to pass the
test.
Error reporting

Error reporting was added to the method Thread::cancel()
Added a simple error management to processes

A simple method for error management was added to the Process::start()
method. The error messages in exception should be checked and corrected
to fit the real reason of the error.
Added the Process::kill() interface

The interface of the Process::kill() method was added to the Process
class
Implemented Process::kill() method

The method was implemented using a new test.
Test for error reporting added

A test for error reporting when signal set to a process is invalid was
added. THis kind of test seems to be the way of testing for errors :)
Error reporting on Process::kill()