Test became flaky in 6

[DarthGandalf]

make -j20 -l20 test TEST_VERBOSE=0                                                                                                                                                                                                                                                
PERL_DL_NONLAZY=1 "/usr/bin/perl" "-MExtUtils::Command::MM" "-MTest::Harness" "-e" "undef *Test::Harness::Switches; test_harness(0, 'blib/lib', 'blib/arch')" t/*.t                                                                                                               
GLib-LOG **: posix_spawn avoided (fd close requested)  at /usr/lib64/perl5/vendor_perl/5.30.3/Gtk3.pm line 555.                                                                                                                                                                   
===(       1;0   1/38  0/4  0/7  0/2   0/10 )===========================GLib-LOG **: posix_spawn avoided (fd close requested)  at /usr/lib64/perl5/vendor_perl/5.30.3/Gtk3.pm line 555.                                                                                           
===(       2;0   1/38  1/4  0/7  0/2   0/10 )===========================GLib-LOG **: posix_spawn avoided (fd close requested)  at /usr/lib64/perl5/vendor_perl/5.30.3/Gtk3.pm line 555.                                                                                           
===(       4;0   1/38  1/4  1/7  0/2   1/10 )===========================GLib-LOG **: posix_spawn avoided (fd close requested)  at /usr/lib64/perl5/vendor_perl/5.30.3/Gtk3.pm line 555.                                                                                           
        Gtk3::init() called at /usr/lib64/perl5/vendor_perl/5.30.3/Gtk3.pm line 2296                                                                                                                                                                                              
        Gtk3::__ANON__() called at /usr/lib64/perl5/vendor_perl/5.30.3/Gtk3.pm line 513                                                                                                                                                                                           
        Gtk3::import("Gtk3", "-init") called at t/4_select.t line 11                                                                                                                                                                                                              
        main::BEGIN() called at t/4_select.t line 11                                                                                                                                                                                                                              
        eval {...} called at t/4_select.t line 11                                                                                                                                                                                                                                 
===(       5;3   1/38  1/4  1/7  1/2   1/10 )===========================LOG **: Name com.canonical.AppMenu.Registrar does not exist on the session bus                                                                                                                            
# PNG of the shown window:                                                                                                                                                                                                                                                        
# iVBORw0KGgoAAAANSUhEUgAAASwAAADIAQAAAAB6pOH4AAAABGdBTUEAALGPC/xhBQAAACBjSFJN                                                                                                                                                                                                    
# AAB6JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAAAmJLR0QAAd2KE6QAAAAHdElN                                                                                                                                                                                                    
# RQfkCxEWLDWpXYKQAAAAHklEQVRYw+3BMQEAAADCoPVPbQdvoAAAAAAAAADgNx54AAEXKN2ZAAAA                                                                                                                                                                                                    
# JXRFWHRkYXRlOmNyZWF0ZQAyMDIwLTExLTE3VDIyOjQ0OjUzKzAwOjAwhU5YPQAAACV0RVh0ZGF0                                                                                                                                                                                                    
# ZTptb2RpZnkAMjAyMC0xMS0xN1QyMjo0NDo1MyswMDowMPQT4IEAAAAASUVORK5CYII=                                                                                                                                                                                                       

#   Failed test 'middle pixel should be green'                                                                                                                                                                                                                                    
#   at t/2_transparent.t line 58.                                                                                                                                                                                                                                                 
#     Structures begin differing at:                                                                                                                                                                                                                                              
#          $got->[1] = '0'                                                                                                                                                                                                                                                        
#     $expected->[1] = '1'                                                                                                                                                                                                                                                        

#   Failed test 'there is red background'                                                                                                                                                                                                                                         
#   at t/2_transparent.t line 71.                                                                                                                                                                                                                                                 
#          got: '0'                                                                                                                                                                                                                                                               
#     expected: '1'                                                                                                                                                                                                                                                               

#   Failed test 'there is blue outside'                                                                                                                                                                                                                                           
#   at t/2_transparent.t line 82.                                                                                                                                                                                                                                                 
#          got: '0'                                                                                                                                                                                                                                                               
#     expected: '1'                                                                                                                                                                                                                                                               
# Looks like you failed 3 tests of 4.                                                                                                                                                                                                                                             
t/2_transparent.t .. Dubious, test returned 3 (wstat 768, 0x300)                                                                                                                                                                                                                  
Failed 3/4 subtests                                                                                                                                                                                                                                                               
t/3_zoom.t ......... ok

Sometimes it still passes though

[DarthGandalf]

This is due to HARNESS_OPTIONS=j20 which was set. Looks like parallel creation several X11 windows can confuse the test. I'll just disable that parallelism on my side.