Update: Problem already found in Re^4: STDERR in Test Results.

Both tests pass but I still get the output to STDERR when the process method is called. I guess I'm just looking for a way to suppress the output...

Or perhaps for a place where someone prints to STDERR or warns.

Looking at B::S::W 1.11 at CPAN, B::S::W::process() calls $self->_error() with the error message shown. And now look at that method:

sub _error {
    my ($self, $message) = @_;
     
    $self->{'error'} = $message;
    if (defined &{$self->{'error'}}) {
        &{$self->{'error'}}($message);
    } else {
        STDERR->print("Stripe Webhook Error: $message\n");
    }
}
[download]

That's why you shall use warn and die instead of printing to STDERR. sub _warning has the same problem.

Oh, by the way: eval catches errors, not warnings, so your variable would be better named $got_error instead of $got_warn.

Alexander