Test exception

---

examples/mocking-functions/exception_snippet.t

$mock->add(get => sub {
    die 'Something went wrong'; 
});
is_deeply $w->count_strings('Beyonce', 'Miley Cyrus'), 
    {
        Beyonce => 0,
        'Miley Cyrus' => 0,
    };

1..2
ok 1
Something went wrong at exception.t line 25.
# Looks like you planned 2 tests but ran 1.
# Looks like your test exited with 255 just after 1.