To enable testing of signal handling, there is a function
tcase_add_test_raise_signal() which is used instead of
tcase_add_test(). This function takes an additional signal
argument, specifying a signal that the test expects to receive. If no
signal is received this is logged as a failure. If a different signal
is received this is logged as an error.
The signal handling functionality only works in CK_FORK mode.