Learned brethren,

I have installed Selenium::Firefox on my linux machine. I have also installed the Firefox browser, geckodriver binary and Xvfb so Firefox can run pseudo-headlessly and a Selenium server is not required. I am trying to run the simplest test script:

use strict; use warnings; use feature 'say';
use Carp::Always;
use Selenium::Firefox;

my $driver = Selenium::Firefox->new;
say 'Binary mode: ' . $driver->binary_mode;

$driver->get('http://www.google.com');
say $driver->get_title;

$driver->shutdown_binary;

__END__
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The module appears to behave as documented in so far as it finds and launches the relevant binaries, according to the process table:

vagrant   1885       00:03 /usr/local/sbin/geckodriver --port 9090 --m
+arionette-port 2828 --binary /usr/lib/firefox/firefox.sh
vagrant   1890       00:02 /usr/lib/firefox/firefox --marionette --pro
+file /tmp/rust_mozprofile.Bezoxqxkgze8
vagrant   1933       00:01 /usr/lib/firefox/plugin-container -greomni 
+/usr/lib/firefox/omni.ja -appomni /usr/lib/firefox/browser/omni.ja -a
+ppdir /usr/lib/firefox/browser 1890 true tab
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But it just hangs then throws an exception when I run it with:

DISPLAY=:42 perl test/selenium.pl
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I get the following error:

Could not create new session:  at .../lib/perl5/Selenium/Remote/Driver
+.pm line 428.
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Working back using the stack trace as a map I found that the code for creating a session in Selenium::Remote::Driver is executed regardless of condition from within BUILD. I can't see any place where that is overridden by the class that extends it (Selenium::Firefox), even though use of that class should by definition rule out a session with the Selenium server.

    if ($self->has_desired_capabilities) {
        $self->new_desired_session( $self->desired_capabilities );
    }
    else {
        # Connect to remote server & establish a new session
        $self->new_session( $self->extra_capabilities );
    }
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I confess I am a bit lost a this point. Thanks for any tips!