When this module checks that the build_requires matches what is required
in my tests, it does not check in my test library files, and so if I
have a module used in a test library and specify that module in
build_requires, this module tells me that I didn't use the required
module in any test. This will fix it:
sub _test_files {
my $self = shift;
return $self->_find_files_by_ext($self->_test_dir, qr/\.t$/),
$self->_pm_files_in_test; # Include test classes
}