Thank you for your comments. Eventually, I was able to pass the tests, making these changes: 
--- t/49-mech-nav.t~    2012-02-12 12:07:33.000000000 +0100
+++ t/49-mech-nav.t     2012-02-12 19:57:38.423630818 +0100
@@ -26,6 +26,8 @@
 
 $mech->get($server->url);
 
+sleep 1;
+
 $mech->click_button(number => 1);
 like( $mech->uri, qr/formsubmit/, 'Clicking on button by number' );
 my $last = $mech->uri;
--- t/51-click_button.t~        2012-02-12 12:07:33.000000000 +0100
+++ t/51-click_button.t 2012-02-12 21:00:45.167679586 +0100
@@ -25,6 +25,7 @@
 my $server = Test::HTTP::LocalServer->spawn();
 
 $mech->get($server->url);
+sleep 1;
 
 my @forms = $mech->forms;
 my $form = $forms[0];
--- t/70-mech-png.t~    2012-02-12 12:07:33.000000000 +0100
+++ t/70-mech-png.t     2012-02-12 21:01:15.651678533 +0100
@@ -41,7 +41,7 @@
         is_deeply $got, $_[1], $_[2]
             or diag Dumper $got;
     } else {
-        SKIP: skip "Image::Info not available", 1;
+        SKIP: { skip "Image::Info not available", 1; }
     };
 };
 
--- t/70-real-status.t~ 2012-02-12 12:07:33.000000000 +0100
+++ t/70-real-status.t  2012-02-12 22:23:40.866996031 +0100
@@ -33,6 +33,7 @@
 t::helper::run_across_instances(\@instances, $instance_port, \&new_me
+ch, sub {
     my ($instance, $mech) = @_;
     $mech->get($server->url);
+    sleep 1;
 
     my $response = $mech->response;
 
--- t/75-save_url-cookies.t~    2012-02-12 12:07:33.000000000 +0100
+++ t/75-save_url-cookies.t     2012-02-13 00:30:03.986919932 +0100
@@ -45,7 +45,7 @@
            $server->url->port,
            undef,
            undef,
-           5, # 5 seconds expiry
+           120, # 2 minutes expiry
 );
 
 my $count;

[download]
Changes 1, 2, and 4 are just 1 second sleeps after a get; change 5 prolongs the cookies to 2 minutes (sometimes, 50 seconds was enough, but sometimes not, 120 is a safe guess). Change 3 makes the SKIP work - last cannot work without a block (2/12 Label not found for "last SKIP" at /usr/lib/perl5/5.14.2/Test/More.pm line 1256.) In some tests, Time::HiRes is used, but not really used.

Especially the cookie thing makes me wonder what could be the cause.

In reply to Re^8: Failing Tests in MozRepl by choroba
in thread Failing Tests in MozRepl by choroba

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