Saint Aardvark's Journal: WWW::Mechanize and the values of testing

One of the great things about going to LISA is that you get the proceedings and/or training for everything on CD or dead tree. (Well, nearly everything...I've heard that some people didn't or couldn't make their training materials available (though I've not been motivated to confirm this yet), and some of the talks didn't do this (Tom, where are your slides?)). There is some wonderful stuff to be found in them...

...like WWW::Mechanize, which is just perfect for testing out this conference registration form I'm working on. Only I've run into a bug that comes when trying to specify which button to click on:

$agent->click_button(value => 'Okay to submit');

That li'l chunk gave me this error:

Can't call method "header" on an undefined value at /home/admin/hugh/perl/lib/perl5/WWW/Mechanize.pm line 2003.

One guy reported the same trouble, but got no response. And the RT queue is fulla spam.

But aha, I found out how to use the Perl debugger in Emacs (M-x perldb. Shhhh!) and was able to track things down. Turns out there are a couple things going on:

1. In the page that I'm parsing, there are actually two forms, not one; one sends you back to correct mistakes, one sends you forward to keep going. Since I was not specifying which one to use, it used the first...and in that one, there is no button labelled "Okay to submit". One I specified the right form ($agent->form_number(2);) everything was good.
2. But of course, this sort of thing shouldn't happen, right? Right.

There are a couple subroutines/methods in this module that aren't testing for the right number of arguments. One of 'em is click_button, which has this loop:

my $request;
.
.
.
elsif ( $args{value} ) {
my $i = 1;
while ( my $input = $form->find_input(undef, 'submit', $i) ) {
if ( $args{value} && ($args{value} eq $input->value) ) {
$request = $input->click( $form, $args{x}, $args{y} );
last;
}
$i++;
} # while
} # $args{value}

return $self->request( $request );

No test/case for not finding a button named whatever, so it just blithely returns $self->request( $request ). But of course, request does the same thing:

sub request {
my $self = shift;
my $request = shift;

$request = $self->_modify_request( $request );

if ( $request->method eq "GET" || $request->method eq "POST" ) {
$self->_push_page_stack();
}

$self->_update_page($request, $self->_make_request( $request, @_ ));
}

Again, no test for the right number of arguments. And having just read the Test::Tutorial manpage, I'm all about unit testing and such, baby.