Bug 43669: Make t::lib::Selenium wait for the server to be ready

This patch adds a wait_for_server_ready check to t::lib::Selenium, so
Selenium-based tests poll the server until it responds successfully
before driving it, instead of assuming it is already up.

This guards against a race we saw on Jenkins CI:
t/db_dependent/selenium/00-onboarding.t and
t/db_dependent/selenium/01-installation.t both failed with 'no such
element: //div[@class="alert alert-success"]' right after the DB
connection check step, immediately after run_tests.pl's
get_commands_to_reset_db() restarted Apache/Plack. That helper
restarts services and moves straight to running the tests with no
readiness wait, so the very first requests can hit workers that are
still warming up. The test then fails on a missing page element even
though there is no bug in the installer flow itself.

A companion issue has been filed against koha-misc4dev to add a
readiness wait to run_tests.pl itself:
https://gitlab.com/koha-community/koha-misc4dev/-/work_items/108

Test plan:
1. Apply the patch
2. Run t/db_dependent/selenium/01-installation.t (or 00-onboarding.t)
   against a fresh empty database with KOHA_TESTING=1, as usual
3. Confirm it still passes normally
4. To exercise the new wait: drop/recreate the database, then run
   "sudo service apache2 restart" and "sudo service koha-common
   restart", then immediately run the selenium test with no delay.
   Confirm it either passes (server came up in time) or fails fast
   with a clear "Cannot wait more for the server to be ready" message
   rather than a confusing missing-element error deep in the install
   wizard

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Pedro Amorim <pedro.amorim@openfifth.co.uk>

t/lib/Selenium.pm

@@ -17,6 +17,7 @@ package t::lib::Selenium;
 
 use Modern::Perl;
 use Carp qw( croak );
+use LWP::UserAgent;
 
 use C4::Context;
 
@@ -47,6 +48,7 @@ sub new {
     bless $self, $class;
     $self->add_error_handler;
     $self->driver->set_implicit_wait_timeout(10000);
+    $self->wait_for_server_ready( $self->{base_url} );
     return $self;
 }
 
@@ -297,6 +299,26 @@ sub click_when_visible {
     $elt->click unless $clicked;    # finally Raise the error
 }
 
+sub wait_for_server_ready {
+    my ( $self, $url ) = @_;
+
+    # CI restarts Apache/Plack right before running Selenium tests, but does not
+    # wait for the workers to finish warming up. Without this, the very first
+    # requests can hit a server that is not fully ready yet, causing pages to
+    # render incompletely.
+    my $ua          = LWP::UserAgent->new( timeout => 5 );
+    my $max_retries = $self->max_retries;
+    my ( $ready, $i );
+    until ($ready) {
+        my $response = eval { $ua->get( $url . 'mainpage.pl' ) };
+        $ready = $response && $response->is_success;
+        sleep 1 unless $ready;
+
+        die "Cannot wait more for the server to be ready ($url)"
+            if $max_retries <= ++$i;
+    }
+}
+
 sub max_retries { 10 }
 
 =head1 NAME
@@ -375,6 +397,14 @@ when we use automation test using Selenium
 
     Wait 10s for an element to be hidden
 
+=head2 wait_for_server_ready
+
+    $s->wait_for_server_ready($url);
+
+    Poll $url (HTTP, outside of the webdriver session) until it responds
+    successfully, up to 10s. Called from the constructor so tests fail fast
+    with a clear error instead of racing a server that is still restarting.
+
 =head2 wait_for_ajax
 
     $s->wait_for_ajax;