diff --git a/UnitTestContrib/lib/Unit/TestApp.pm b/UnitTestContrib/lib/Unit/TestApp.pm
index 34e45e5fd9..84628b3347 100644
--- a/UnitTestContrib/lib/Unit/TestApp.pm
+++ b/UnitTestContrib/lib/Unit/TestApp.pm
@@ -113,7 +113,7 @@ sub registerCallbacks {
     $this->_cbRegistered(1);
 }
 
-before _prepareConfig => sub {
+before BUILD => sub {
     my $this = shift;
 
     $this->registerCallbacks;
diff --git a/UnitTestContrib/test/unit/FoswikiFnTestCase.pm b/UnitTestContrib/test/unit/FoswikiFnTestCase.pm
index 28cce9e07e..d68b2abf5e 100644
--- a/UnitTestContrib/test/unit/FoswikiFnTestCase.pm
+++ b/UnitTestContrib/test/unit/FoswikiFnTestCase.pm
@@ -31,8 +31,7 @@ use Foswiki::UI::Register();
 use Try::Tiny;
 use Carp qw(cluck);
 
-use Moo;
-use namespace::clean;
+use Foswiki::Class;
 extends qw(FoswikiTestCase);
 
 has test_user_forename => ( is => 'rw', );
diff --git a/UnitTestContrib/test/unit/ManageDotPmTests.pm b/UnitTestContrib/test/unit/ManageDotPmTests.pm
index 1963ecd85a..cd3f611a84 100644
--- a/UnitTestContrib/test/unit/ManageDotPmTests.pm
+++ b/UnitTestContrib/test/unit/ManageDotPmTests.pm
@@ -225,7 +225,7 @@ sub _registerUserException {
             },
         },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
     my $exception;
     try {
         $this->captureWithKey(
@@ -252,7 +252,7 @@ sub _registerUserException {
 
     # Reload caches
     $this->createNewFoswikiApp;
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     return $exception;
 }
@@ -814,7 +814,7 @@ sub verify_resetEmailOkay {
         callbacks => { handleRequestException => \&_cbHRE, },
     );
 
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
     try {
         $this->captureWithKey(
             manage => sub {
@@ -923,7 +923,7 @@ EOM
         callbacks => { handleRequestException => \&_cbHRE, },
     );
 
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     # SMELL We've set path_info, web and topic must be set from it.
     #$req->topic($regTopic);
@@ -1071,7 +1071,7 @@ EOM
         callbacks => { handleRequestException => \&_cbHRE, },
     );
 
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         my ($text) = $this->captureWithKey(
@@ -1133,7 +1133,7 @@ sub verify_deleteUser {
         callbacks => { handleRequestException => \&_cbHRE, },
     );
 
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1454,7 +1454,7 @@ sub test_createDefaultWeb {
         callbacks => { handleRequestException => \&_cbHRE, },
     );
 
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         my ( $stdout, $stderr, $result ) =
@@ -1837,7 +1837,7 @@ sub test_createEmptyWeb {
         callbacks => { handleRequestException => \&_cbHRE, },
     );
 
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         my ( $stdout, $stderr, $result ) =
diff --git a/UnitTestContrib/test/unit/RegisterTests.pm b/UnitTestContrib/test/unit/RegisterTests.pm
index 2b25a2a705..884cfae8d5 100644
--- a/UnitTestContrib/test/unit/RegisterTests.pm
+++ b/UnitTestContrib/test/unit/RegisterTests.pm
@@ -3,7 +3,7 @@ use v5.14;
 
 package Foswiki::Exception::RTInfo;
 
-use Moo;
+use Foswiki::Class;
 extends qw(Foswiki::Exception);
 
 has template => ( is => 'rw', );
@@ -20,7 +20,6 @@ use diagnostics;
 #Uncomment to isolate
 #our @TESTS = qw(notest_registerVerifyOk); #notest_UnregisteredUser);
 
-use Foswiki::UI::Register();
 use Data::Dumper;
 use FileHandle();
 use File::Copy();
@@ -32,8 +31,7 @@ use Try::Tiny;
 # Note that the FoswikiFnTestCase needs to use the registration code to work,
 # so this is a bit arse before tit. However we need some pre-registered users
 # for this to work sensibly, so we just have to bite the bullet.
-use Moo;
-use namespace::clean;
+use Foswiki::Class;
 extends qw( FoswikiFnTestCase );
 
 has regUI => (
@@ -189,7 +187,7 @@ EOF
         Foswiki::Exception::Fatal->rethrow($_);
     };
 
-    @FoswikiFnTestCase::mails = ();
+    @Unit::FoswikiTestRole::mails = ();
 
     return;
 };
@@ -262,7 +260,7 @@ sub registerAccount {
     );
     $cfgData = $this->app->cfg->data;
 
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->regUI->_action_verify;
@@ -274,9 +272,10 @@ sub registerAccount {
                 $this->assert_str_equals( $REG_TMPL, $e->template,
                     $e->stringify() );
                 $this->assert_str_equals( "thanks", $e->def, $e->stringify() );
-                $this->assert_equals( 2, scalar(@FoswikiFnTestCase::mails) );
+                $this->assert_equals( 2,
+                    scalar(@Unit::FoswikiTestRole::mails) );
                 my $done = '';
-                foreach my $mail (@FoswikiFnTestCase::mails) {
+                foreach my $mail (@Unit::FoswikiTestRole::mails) {
                     if ( $mail->header('Subject') =~ m/Registration for/m ) {
                         my $new_user_email = $this->new_user_email;
                         if ( $mail->header('To') =~ m/\b$new_user_email\b/m ) {
@@ -295,7 +294,7 @@ qr/$cfgData->{WebMasterName} <$cfgData->{WebMasterEmail}>/,
                     }
                 }
                 $this->assert($done);
-                @FoswikiFnTestCase::mails = ();
+                @Unit::FoswikiTestRole::mails = ();
             }
             else {
                 $e->rethrow;
@@ -707,7 +706,7 @@ sub registerVerifyOk {
         callbacks => { handleRequestException => \&_cbHRE },
     );
     $cfgData = $this->app->cfg->data;
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -751,7 +750,7 @@ sub registerVerifyOk {
 
     $cfgData = $this->app->cfg->data;
     $this->app->heap->{DebugVerificationCode} = $code;
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     $code = $this->app->request->param('code');
     my $data = $this->regUI->_loadPendingRegistration($code);
@@ -759,9 +758,9 @@ sub registerVerifyOk {
     $this->assert_equals( $data->{VerificationCode}, $code );
     $this->assert( $data->{Email} );
 
-    $this->assert_equals( 1, scalar(@FoswikiFnTestCase::mails) );
+    $this->assert_equals( 1, scalar(@Unit::FoswikiTestRole::mails) );
     my $done = '';
-    foreach my $mail (@FoswikiFnTestCase::mails) {
+    foreach my $mail (@Unit::FoswikiTestRole::mails) {
         my $body = $mail->body();
         if ( $body =~ m/Your verification code is /m ) {
             $this->assert( !$done, $done . "\n---------\n" . $body );
@@ -773,7 +772,7 @@ sub registerVerifyOk {
         #}
     }
     $this->assert($done);
-    @FoswikiFnTestCase::mails = ();
+    @Unit::FoswikiTestRole::mails = ();
 
     # We're sitting with a valid verification code waiting for the next step
     # i.e. need to _verify
@@ -830,7 +829,7 @@ sub _registerBadVerify {
     );
     $cfgData = $this->app->cfg->data;
 
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
     try {
         $this->captureWithKey(
             register => sub { return $this->app->handleRequest; }, );
@@ -869,7 +868,7 @@ sub _registerBadVerify {
     );
 
     $cfgData = $this->app->cfg->data;
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->regUI->_action_verify;
@@ -892,8 +891,8 @@ sub _registerBadVerify {
                 text => "Expected a redirect but received: " . $e );
         }
     };
-    $this->assert_equals( 1, scalar(@FoswikiFnTestCase::mails) );
-    my $mess = $FoswikiFnTestCase::mails[0];
+    $this->assert_equals( 1, scalar(@Unit::FoswikiTestRole::mails) );
+    my $mess = $Unit::FoswikiTestRole::mails[0];
     $this->assert_matches(
         qr/$cfgData->{WebMasterName} <$cfgData->{WebMasterEmail}>/,
         $mess->header('From') );
@@ -960,7 +959,7 @@ sub _registerNoVerifyOk {
         callbacks => { handleRequestException => \&_cbHRE },
     );
 
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -972,9 +971,9 @@ sub _registerNoVerifyOk {
             $this->assert_str_equals( $REG_TMPL, $e->template,
                 $e->stringify() );
             $this->assert_str_equals( "thanks", $e->def, $e->stringify() );
-            $this->assert_equals( 2, scalar(@FoswikiFnTestCase::mails) );
+            $this->assert_equals( 2, scalar(@Unit::FoswikiTestRole::mails) );
             my $done = '';
-            foreach my $mail (@FoswikiFnTestCase::mails) {
+            foreach my $mail (@Unit::FoswikiTestRole::mails) {
                 if ( $mail->header('Subject') =~ m/^.*Registration for/m ) {
                     my $new_user_email = $this->new_user_email;
                     if ( $mail->header('To') =~ m/^.*\b$new_user_email\b/m ) {
@@ -994,7 +993,7 @@ qr/$cfgData->{WebMasterName} <$cfgData->{WebMasterEmail}>/,
                 }
             }
             $this->assert($done);
-            @FoswikiFnTestCase::mails = ();
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -1043,7 +1042,7 @@ sub verify_rejectShortPassword {
         },
         callbacks => { handleRequestException => \&_cbHRE },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1056,8 +1055,8 @@ sub verify_rejectShortPassword {
                 $e->stringify() );
             $this->assert_str_equals( "bad_password", $e->def,
                 $e->stringify() );
-            $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
-            @FoswikiFnTestCase::mails = ();
+            $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -1107,7 +1106,7 @@ sub verify_userTopictemplate {
         },
         callbacks => { handleRequestException => \&_cbHRE },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1120,8 +1119,8 @@ sub verify_userTopictemplate {
                 $e->stringify() );
             $this->assert_str_equals( "bad_templatetopic", $e->def,
                 $e->stringify() );
-            $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
-            @FoswikiFnTestCase::mails = ();
+            $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -1157,7 +1156,7 @@ sub verify_userTopictemplate {
         },
         callbacks => { handleRequestException => \&_cbHRE },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1236,7 +1235,7 @@ sub verify_rejectDuplicateEmail {
         },
         callbacks => { handleRequestException => \&_cbHRE },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1248,9 +1247,9 @@ sub verify_rejectDuplicateEmail {
             $this->assert_str_equals( $REG_TMPL, $e->template,
                 $e->stringify() );
             $this->assert_str_equals( "thanks", $e->def, $e->stringify() );
-            $this->assert_equals( 2, scalar(@FoswikiFnTestCase::mails) );
+            $this->assert_equals( 2, scalar(@Unit::FoswikiTestRole::mails) );
             my $done = '';
-            foreach my $mail (@FoswikiFnTestCase::mails) {
+            foreach my $mail (@Unit::FoswikiTestRole::mails) {
                 if ( $mail->header('Subject') =~ m/^.*Registration for/m ) {
                     if ( $mail->header('To') =~ m/^.*\bjoe\@gooddomain.net\b/m )
                     {
@@ -1270,7 +1269,7 @@ qr/$cfgData->{WebMasterName} <$cfgData->{WebMasterEmail}>/,
                 }
             }
             $this->assert($done);
-            @FoswikiFnTestCase::mails = ();
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -1305,7 +1304,7 @@ qr/$cfgData->{WebMasterName} <$cfgData->{WebMasterEmail}>/,
         },
         callbacks => { handleRequestException => \&_cbHRE },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1317,8 +1316,8 @@ qr/$cfgData->{WebMasterName} <$cfgData->{WebMasterEmail}>/,
             $this->assert_str_equals( $REG_TMPL, $e->template,
                 $e->stringify() );
             $this->assert_str_equals( "dup_email", $e->def, $e->stringify() );
-            $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
-            @FoswikiFnTestCase::mails = ();
+            $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -1368,7 +1367,7 @@ sub verify_rejectDuplicatePendingEmail {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1382,7 +1381,7 @@ sub verify_rejectDuplicatePendingEmail {
             $this->assert_str_equals( "confirm", $e->def, $e->stringify() );
             $this->assert_matches( 'joe@dupdomain.net', $e->params->[0],
                 $e->stringify() );
-            @FoswikiFnTestCase::mails = ();
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -1409,7 +1408,7 @@ sub verify_rejectDuplicatePendingEmail {
     #
     #$query->path_info( "/" . $this->users_web . "/UserRegistration" );
     #$this->createNewFoswikiSession( $cfgData->{DefaultUserLogin}, $query );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
     $cfgData->{Register}{NeedVerification} = 1;
     $cfgData->{Register}{UniqueEmail}      = 1;
 
@@ -1427,8 +1426,8 @@ sub verify_rejectDuplicatePendingEmail {
             $this->assert_str_equals( $REG_TMPL, $e->template,
                 $e->stringify() );
             $this->assert_str_equals( "dup_email", $e->def, $e->stringify() );
-            $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
-            @FoswikiFnTestCase::mails = ();
+            $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -1480,7 +1479,7 @@ sub verify_rejectFilteredEmail {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1492,8 +1491,8 @@ sub verify_rejectFilteredEmail {
             $this->assert_str_equals( $REG_TMPL, $e->template,
                 $e->stringify() );
             $this->assert_str_equals( "rej_email", $e->def, $e->stringify() );
-            $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
-            @FoswikiFnTestCase::mails = ();
+            $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -1528,7 +1527,7 @@ sub verify_rejectFilteredEmail {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1540,9 +1539,9 @@ sub verify_rejectFilteredEmail {
             $this->assert_str_equals( $REG_TMPL, $e->template,
                 $e->stringify() );
             $this->assert_str_equals( "thanks", $e->def, $e->stringify() );
-            $this->assert_equals( 2, scalar(@FoswikiFnTestCase::mails) );
+            $this->assert_equals( 2, scalar(@Unit::FoswikiTestRole::mails) );
             my $done = '';
-            foreach my $mail (@FoswikiFnTestCase::mails) {
+            foreach my $mail (@Unit::FoswikiTestRole::mails) {
                 if ( $mail->header('Subject') =~ m/^.*Registration for/m ) {
                     if ( $mail->header('To') =~ m/^.*\bjoe\@gooddomain.net\b/m )
                     {
@@ -1562,7 +1561,7 @@ qr/$cfgData->{WebMasterName} <$cfgData->{WebMasterEmail}>/,
                 }
             }
             $this->assert($done);
-            @FoswikiFnTestCase::mails = ();
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -1611,7 +1610,7 @@ sub verify_rejectEvilContent {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1624,7 +1623,7 @@ sub verify_rejectEvilContent {
 
             $this->assert_matches(
 qr/.*Comment: &#60;blah&#62;.*Organization: &#60;script&#62;Bad stuff&#60;\/script&#62;/ms,
-                $FoswikiFnTestCase::mails[0]->body()
+                $Unit::FoswikiTestRole::mails[0]->body()
             );
 
             my ($meta) = Foswiki::Func::readTopic( $cfgData->{UsersWebName},
@@ -1681,7 +1680,7 @@ sub verify_shortPassword {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1699,10 +1698,10 @@ sub verify_shortPassword {
                 $e->stringify() );
             $this->assert_str_equals( "bad_password", $e->def,
                 $e->stringify() );
-            $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
+            $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
 
-# don't check the FoswikiFnTestCase::mails in this test case - this is done elsewhere
-            @FoswikiFnTestCase::mails = ();
+# don't check the Unit::FoswikiTestRole::mails in this test case - this is done elsewhere
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -1748,7 +1747,7 @@ sub verify_duplicateActivation {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
     try {
         $this->captureWithKey(
             register => sub { return $this->app->handleRequest; }, );
@@ -1793,7 +1792,7 @@ sub verify_duplicateActivation {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1814,7 +1813,7 @@ sub verify_duplicateActivation {
     };
 
     # and now for something completely different: Do it all over again
-    @FoswikiFnTestCase::mails = ();
+    @Unit::FoswikiTestRole::mails = ();
 
     $this->createNewFoswikiApp(
         requestParams => {
@@ -1833,7 +1832,7 @@ sub verify_duplicateActivation {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1846,7 +1845,7 @@ sub verify_duplicateActivation {
                 $e->stringify() );
             $this->assert_str_equals( "duplicate_activation", $e->def,
                 $e->stringify() );
-            $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
+            $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -1854,7 +1853,7 @@ sub verify_duplicateActivation {
             $e->rethrow;
         }
     };
-    @FoswikiFnTestCase::mails = ();
+    @Unit::FoswikiTestRole::mails = ();
 
     return;
 }
@@ -1899,7 +1898,7 @@ sub verify_resetPasswordOkay {
         },
         callbacks => { handleRequestException => \&_cbHRE },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1918,8 +1917,8 @@ sub verify_resetPasswordOkay {
             $e->rethrow;
         }
     };
-    $this->assert_equals( 1, scalar(@FoswikiFnTestCase::mails) );
-    my $mess = $FoswikiFnTestCase::mails[0];
+    $this->assert_equals( 1, scalar(@Unit::FoswikiTestRole::mails) );
+    my $mess = $Unit::FoswikiTestRole::mails[0];
     $this->assert_matches(
         qr/$cfgData->{WebMasterName} <$cfgData->{WebMasterEmail}>/,
         $mess->header('From') );
@@ -1958,7 +1957,7 @@ sub verify_resetPasswordNoSuchUser {
         },
         callbacks => { handleRequestException => \&_cbHRE },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -1977,7 +1976,7 @@ sub verify_resetPasswordNoSuchUser {
             $e->rethrow;
         }
     };
-    $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
+    $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
 
     return;
 }
@@ -2007,7 +2006,7 @@ sub verify_resetPasswordNeedPrivilegeForMultipleReset {
         },
         callbacks => { handleRequestException => \&_cbHRE },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -2027,7 +2026,7 @@ sub verify_resetPasswordNeedPrivilegeForMultipleReset {
             $e->rethrow;
         }
     };
-    $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
+    $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
 
     return;
 }
@@ -2063,7 +2062,7 @@ sub verify_resetPasswordNoPassword {
         },
         callbacks => { handleRequestException => \&_cbHRE },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -2084,8 +2083,8 @@ sub verify_resetPasswordNoPassword {
     };
 
     # If the user is not in htpasswd, there's can't be an email
-    $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
-    @FoswikiFnTestCase::mails = ();
+    $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
+    @Unit::FoswikiTestRole::mails = ();
 
     return;
 }
@@ -2131,7 +2130,7 @@ sub verify_UnregisteredUser {
     };
 
     # $this->assert_null( UnregisteredUser::reloadUserContext($code));
-    $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
+    $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
 
     return;
 }
@@ -2208,7 +2207,7 @@ sub verify_buildRegistrationEmail {
 
     $this->createNewFoswikiApp( engineParams =>
           { initialAttributes => { user => $cfgData->{DefaultUserLogin}, }, } );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     my $actual =
       $this->regUI->_buildConfirmationEmail( \%data,
@@ -2234,7 +2233,7 @@ sub verify_buildRegistrationEmail {
     $this->assert( $actual =~ m/^\s*\*\s*Name:\s*$new_user_fullname$/,
         $actual );
 
-    $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
+    $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
 
     return;
 }
@@ -2290,7 +2289,7 @@ sub verify_disabled_registration {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -2349,7 +2348,7 @@ sub test_PendingRegistrationManualCleanup {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -2422,7 +2421,7 @@ sub test_PendingRegistrationAutoCleanup {
 
     );
     $cfgData = $this->app->cfg->data;
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -2452,12 +2451,12 @@ sub test_PendingRegistrationAutoCleanup {
     utime( $mtime, $mtime, $file )
       || $this->assert( 0, "couldn't touch $file: $!" );
 
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
-        no strict 'refs';
         $this->captureWithKey(
             register => sub { return $this->app->handleRequest; }, );
+        $this->reCreateFoswikiApp;
         $this->captureWithKey(
             register => sub { return $this->app->handleRequest; }, );
     }
@@ -2514,7 +2513,7 @@ sub test_Item12205 {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -2584,7 +2583,7 @@ sub test_3951 {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -2648,7 +2647,7 @@ sub test_4061 {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     $this->assert(
         open( my $fh, "<:encoding(utf-8)", $cfgData->{Htpasswd}{FileName} ) );
@@ -2768,7 +2767,7 @@ sub verify_resetPassword_NoWikiUsersEntry {
         callbacks => { handleRequestException => \&_cbHRE },
 
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->captureWithKey(
@@ -2787,8 +2786,8 @@ sub verify_resetPassword_NoWikiUsersEntry {
             $e->rethrow;
         }
     };
-    $this->assert_equals( 1, scalar(@FoswikiFnTestCase::mails) );
-    my $mess = $FoswikiFnTestCase::mails[0];
+    $this->assert_equals( 1, scalar(@Unit::FoswikiTestRole::mails) );
+    my $mess = $Unit::FoswikiTestRole::mails[0];
     $this->assert_matches(
         qr/$cfgData->{WebMasterName} <$cfgData->{WebMasterEmail}>/,
         $mess->header('From') );
@@ -2832,7 +2831,7 @@ sub registerUserException {
         },
         callbacks => { handleRequestException => \&_cbHRE },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
     my $exception;
     try {
         $this->captureWithKey(
@@ -2867,7 +2866,7 @@ sub registerUserException {
 
     # Reload caches
     $this->reCreateFoswikiApp;
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     return $exception;
 }
@@ -3085,7 +3084,7 @@ sub verify_registerVerifyOKApproved {
     # setting was established, and will always have a LoginName
     $this->registerUserException( 'asdf', 'Rego', 'Approver',
         'approve@example.com' );
-    @FoswikiFnTestCase::mails = ();
+    @Unit::FoswikiTestRole::mails = ();
 
     $cfgData->{Register}{NeedVerification} = 1;
 
@@ -3111,7 +3110,7 @@ sub verify_registerVerifyOKApproved {
 
     );
     $cfgData = $this->app->cfg->data;
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     $cfgData->{Register}{NeedApproval} = 1;
     $cfgData->{Register}{Approvers}    = 'RegoApprover';
@@ -3124,8 +3123,8 @@ sub verify_registerVerifyOKApproved {
             $this->assert_str_equals( $REG_TMPL, $e->template,
                 $e->stringify() );
             $this->assert_str_equals( "approve", $e->def );
-            $this->assert_equals( 1, scalar(@FoswikiFnTestCase::mails) );
-            foreach my $mail (@FoswikiFnTestCase::mails) {
+            $this->assert_equals( 1, scalar(@Unit::FoswikiTestRole::mails) );
+            foreach my $mail (@Unit::FoswikiTestRole::mails) {
                 $this->assert_matches( qr/registration approval required/m,
                     $mail->header('Subject') );
                 $this->assert_matches( qr/RegoApprover <approve\@example.com>/m,
@@ -3141,7 +3140,7 @@ sub verify_registerVerifyOKApproved {
                 $this->assert_equals( $this->app->heap->{DebugVerificationCode},
                     $1 );
             }
-            @FoswikiFnTestCase::mails = ();
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -3166,8 +3165,11 @@ sub verify_registerVerifyOKApproved {
         },
         callbacks => { handleRequestException => \&_cbHRE },
 
-        # Preserve the heap data.
-        heap => $this->_cloneData( $this->app->heap, 'heap' ),
+        # Preserve the heap data Debug.* keys.
+        heap => {
+            map { $_ => $this->app->heap->{$_} }
+            grep { /^Debug/ } keys %{ $this->app->heap }
+        },
     );
 
     # Make sure we get bounced unless we are logged in
@@ -3195,9 +3197,14 @@ sub verify_registerVerifyOKApproved {
             },
         },
         callbacks => { handleRequestException => \&_cbHRE },
-        heap => $this->_cloneData( $this->app->heap, 'heap' ),
+
+        # Preserve the heap data Debug.* keys.
+        heap => {
+            map { $_ => $this->app->heap->{$_} }
+            grep { /^Debug/ } keys %{ $this->app->heap }
+        },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->regUI->_action_approve;
@@ -3212,8 +3219,8 @@ sub verify_registerVerifyOKApproved {
             $this->assert_str_equals( "rego_approved", $e->def );
 
        # Make sure the confirmations are sent; one to the user, one to the admin
-            $this->assert_equals( 2, scalar(@FoswikiFnTestCase::mails) );
-            foreach my $mail (@FoswikiFnTestCase::mails) {
+            $this->assert_equals( 2, scalar(@Unit::FoswikiTestRole::mails) );
+            foreach my $mail (@Unit::FoswikiTestRole::mails) {
                 if ( $mail->header('To') =~ m/^Wiki/m ) {
                     $this->assert_matches( qr/^Wiki Administrator/m,
                         $mail->header('To') );
@@ -3226,7 +3233,7 @@ sub verify_registerVerifyOKApproved {
                     qr/^Foswiki - Registration for WalterPigeon/m,
                     $mail->header('Subject') );
             }
-            @FoswikiFnTestCase::mails = ();
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -3255,7 +3262,7 @@ sub verify_registerVerifyOKDisapproved {
     # setting was established, and will always have a LoginName
     $this->registerUserException( 'asdf', 'Rego', 'Approver',
         'approve@example.com' );
-    @FoswikiFnTestCase::mails = ();
+    @Unit::FoswikiTestRole::mails = ();
 
     $cfgData->{Register}{NeedVerification} = 1;
 
@@ -3281,7 +3288,7 @@ sub verify_registerVerifyOKDisapproved {
 
     );
     $cfgData = $this->app->cfg->data;
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     $cfgData->{Register}{NeedApproval} = 1;
     $cfgData->{Register}{Approvers}    = 'RegoApprover';
@@ -3294,8 +3301,8 @@ sub verify_registerVerifyOKDisapproved {
             $this->assert_str_equals( $REG_TMPL, $e->template,
                 $e->stringify() );
             $this->assert_str_equals( "approve", $e->def );
-            $this->assert_equals( 1, scalar(@FoswikiFnTestCase::mails) );
-            foreach my $mail (@FoswikiFnTestCase::mails) {
+            $this->assert_equals( 1, scalar(@Unit::FoswikiTestRole::mails) );
+            foreach my $mail (@Unit::FoswikiTestRole::mails) {
                 $this->assert_matches( qr/^.* registration approval required/m,
                     $mail->header('Subject') );
                 $this->assert_matches(
@@ -3312,7 +3319,7 @@ sub verify_registerVerifyOKDisapproved {
                 $this->assert_equals( $this->app->heap->{DebugVerificationCode},
                     $1 );
             }
-            @FoswikiFnTestCase::mails = ();
+            @Unit::FoswikiTestRole::mails = ();
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
@@ -3338,7 +3345,7 @@ sub verify_registerVerifyOKDisapproved {
         },
         callbacks => { handleRequestException => \&_cbHRE },
     );
-    $this->app->net->setMailHandler( \&FoswikiFnTestCase::sentMail );
+    $this->app->net->setMailHandler( $this->can('sentMail') );
 
     try {
         $this->regUI->_action_disapprove;
@@ -3353,7 +3360,7 @@ sub verify_registerVerifyOKDisapproved {
             $this->assert_str_equals( "rego_denied", $e->def );
 
             # Make sure no mails are sent (yet)
-            $this->assert_equals( 0, scalar(@FoswikiFnTestCase::mails) );
+            $this->assert_equals( 0, scalar(@Unit::FoswikiTestRole::mails) );
         }
         else {
             $e->_set_text( "expected an oops redirect but received: "
diff --git a/core/lib/Foswiki/App.pm b/core/lib/Foswiki/App.pm
index 8fb55a3b2c..4ebfc24de7 100644
--- a/core/lib/Foswiki/App.pm
+++ b/core/lib/Foswiki/App.pm
@@ -584,7 +584,6 @@ sub handleRequest {
     };
 
     my $return = $res->as_array;
-    $res->outputHasStarted(1);
     $rc = $this->engine->finalizeReturn($return);
 
     # Clean up sessions before we finish.
diff --git a/core/lib/Foswiki/AppObject.pm b/core/lib/Foswiki/AppObject.pm
index 7daa678d54..421ffcc5d0 100644
--- a/core/lib/Foswiki/AppObject.pm
+++ b/core/lib/Foswiki/AppObject.pm
@@ -17,7 +17,6 @@ Method create() is imported from Foswiki::App class.
 =cut
 
 use Assert;
-use Foswiki::Exception;
 
 require Foswiki::Object;
 
diff --git a/core/lib/Foswiki/Attach.pm b/core/lib/Foswiki/Attach.pm
index 97411e83ca..ff10ab6129 100644
--- a/core/lib/Foswiki/Attach.pm
+++ b/core/lib/Foswiki/Attach.pm
@@ -15,10 +15,8 @@ use Assert;
 use Unicode::Normalize;
 use Foswiki qw(expandStandardEscapes);
 
-use Moo;
-use namespace::clean;
+use Foswiki::Class qw(app);
 extends qw(Foswiki::Object);
-with qw(Foswiki::AppObject);
 
 BEGIN {
     if ( $Foswiki::cfg{UseLocale} ) {
diff --git a/core/lib/Foswiki/Class.pm b/core/lib/Foswiki/Class.pm
index f6ab61557b..a1e593789b 100644
--- a/core/lib/Foswiki/Class.pm
+++ b/core/lib/Foswiki/Class.pm
@@ -125,7 +125,8 @@ sub import {
         if ( exists $options{$param} ) {
             my $opt = $options{$param};
             $opt->{use} = 1;
-            push @noNsClean, @{ $opt->{keywords} } if defined $opt->{keywords};
+
+            #push @noNsClean, @{ $opt->{keywords} } if defined $opt->{keywords};
         }
         else {
             push @p, $param;
@@ -146,6 +147,7 @@ sub import {
     require feature;
     feature->import($featureSet);
 
+    require namespace::clean;
     namespace::clean->import(
         -cleanee => $target,
         -except  => \@noNsClean,
@@ -178,20 +180,22 @@ sub _assign_role {
     push @{ $_assignedRoles{$class} }, $role;
 }
 
+sub _handler_callback_names {
+    my $target = caller;
+    Foswiki::Aux::Callbacks::registerCallbackNames( $target, @_ );
+}
+
 sub _install_callbacks {
     my ( $class, $target ) = @_;
 
+    Foswiki::load_package('Foswiki::Aux::Callbacks');
     _assign_role( $target, 'Foswiki::Aux::Callbacks' );
-    _inject_code( $target, "callback_names", \&_handler_callbacks );
-}
-
-sub _handler_callbacks (@) {
-    my $target = caller;
-    Foswiki::Aux::Callbacks::registerCallbackNames( $target, @_ );
+    _inject_code( $target, "callback_names", *_handler_callback_names );
 }
 
 sub _install_app {
     my ( $class, $target ) = @_;
+    Foswiki::load_package('Foswiki::AppObject');
     _assign_role( $target, 'Foswiki::AppObject' );
 }
 
diff --git a/core/lib/Foswiki/Configure/Auth.pm b/core/lib/Foswiki/Configure/Auth.pm
index 18bd24f90b..9ca302355e 100644
--- a/core/lib/Foswiki/Configure/Auth.pm
+++ b/core/lib/Foswiki/Configure/Auth.pm
@@ -2,9 +2,11 @@
 
 package Foswiki::Configure::Auth;
 
+use strict;
+use warnings;
+
 use Foswiki::Func;
 use Foswiki::AccessControlException;
-use Foswiki::Contrib::JsonRpcContrib::Error;
 
 =begin TML
 
@@ -14,9 +16,6 @@ Implements authorization checking for access to configure.
 
 =cut
 
-use strict;
-use warnings;
-
 =begin TML
 
 ---++ StaticMethod checkAccess( $app, $die )
@@ -53,6 +52,12 @@ sub checkAccess {
         }
         unless ($authorized) {
             if ($json) {
+
+                # NOTE Don't pre-load this module because it'll break
+                # tools/configure when JsonRpcContrib isn't installed
+                # (yet).
+                Foswiki::load_package(
+                    "Foswiki::Contrib::JsonRpcContrib::Error");
                 throw Foswiki::Contrib::JsonRpcContrib::Error( -32600,
 'Access to configure denied by {FeatureAccess}{Configure} Setting'
                 );
@@ -71,6 +76,8 @@ sub checkAccess {
     else {
         unless ( Foswiki::Func::isAnAdmin() ) {
             if ($json) {
+                Foswiki::load_package(
+                    "Foswiki::Contrib::JsonRpcContrib::Error");
                 throw Foswiki::Contrib::JsonRpcContrib::Error( -32600,
                     'Access to configure denied for non-admin users' );
             }
diff --git a/core/lib/Foswiki/Engine.pm b/core/lib/Foswiki/Engine.pm
index 6d121f3b72..033a77d3f7 100644
--- a/core/lib/Foswiki/Engine.pm
+++ b/core/lib/Foswiki/Engine.pm
@@ -20,10 +20,8 @@ use Assert;
 use Scalar::Util ();
 use Unicode::Normalize;
 
-use Moo;
-use namespace::clean;
+use Foswiki::Class qw(app);
 extends qw(Foswiki::Object);
-with qw(Foswiki::AppObject);
 
 use constant HTTP_COMPLIANT => undef;    # This is a generic class.
 
diff --git a/core/lib/Foswiki/Engine/CGI.pm b/core/lib/Foswiki/Engine/CGI.pm
index e76bb60598..b960ca5031 100644
--- a/core/lib/Foswiki/Engine/CGI.pm
+++ b/core/lib/Foswiki/Engine/CGI.pm
@@ -384,6 +384,9 @@ around stringifyHeaders => sub {
 around write => sub {
     my $orig = shift;
     my ( $this, $buffer ) = @_;
+
+    # This is the only location where we know EXACTLY that output has started.
+    $this->response->outputHasStarted(1);
     print $buffer;
 };
 
diff --git a/core/lib/Foswiki/Engine/PSGI.pm b/core/lib/Foswiki/Engine/PSGI.pm
index 13538fd396..cca9c3a1b3 100644
--- a/core/lib/Foswiki/Engine/PSGI.pm
+++ b/core/lib/Foswiki/Engine/PSGI.pm
@@ -17,8 +17,7 @@ use Assert;
 use Plack::Request;
 use Unicode::Normalize;
 
-use Moo;
-use namespace::clean;
+use Foswiki::Class;
 extends qw(Foswiki::Engine);
 
 use constant HTTP_COMPLIANT => 1;
diff --git a/core/lib/Foswiki/Exception.pm b/core/lib/Foswiki/Exception.pm
index 460d3cb17a..f7072cacaa 100644
--- a/core/lib/Foswiki/Exception.pm
+++ b/core/lib/Foswiki/Exception.pm
@@ -59,13 +59,6 @@ with 'Throwable';
 
 our $EXCEPTION_TRACE = 0;
 
-BEGIN {
-    if ( $Foswiki::cfg{UseLocale} ) {
-        require locale;
-        import locale();
-    }
-}
-
 =begin TML
 
 ---++ ObjectAttribute file
@@ -509,11 +502,8 @@ Attributes:
 
 package Foswiki::Exception::HTTPResponse;
 use Foswiki::Class;
-use namespace::clean;
 extends qw(Foswiki::Exception);
 
-our @_newParameters = qw(status reason response);
-
 has status =>
   ( is => 'ro', lazy => 1, default => sub { $_[0]->response->status, }, );
 has response => (
@@ -562,7 +552,6 @@ use CGI ();
 use Assert;
 
 use Foswiki::Class;
-use namespace::clean;
 extends qw(Foswiki::Exception::HTTPResponse);
 
 has header => ( is => 'rw', default => '' );
diff --git a/core/lib/Foswiki/Net.pm b/core/lib/Foswiki/Net.pm
index 4b5fe40333..ffa0bee803 100644
--- a/core/lib/Foswiki/Net.pm
+++ b/core/lib/Foswiki/Net.pm
@@ -21,10 +21,8 @@ use URI;
 
 use Foswiki::IP qw/:regexp :info $IPv6Avail/;
 
-use Moo;
-use namespace::clean;
+use Foswiki::Class qw(app);
 extends qw(Foswiki::Object);
-with qw(Foswiki::AppObject);
 
 BEGIN {
     if ( $Foswiki::cfg{UseLocale} ) {
@@ -302,7 +300,7 @@ sub getExternalResource {
         }
     }
     catch {
-        my $message = ref($_) ? $_->stringify : $_;
+        my $message = Foswiki::Exception::errorStr($_);
         $response =
           $this->create( 'Foswiki::Net::HTTPResponse', message => $message );
     };
@@ -350,6 +348,8 @@ sub _logMailError {
     my $this  = shift;
     my $level = shift;
 
+    my $cfgData = $this->app->cfg->data;
+
     my $msg = join( '', @_ );
     chomp $msg;
 
@@ -361,7 +361,7 @@ sub _logMailError {
         $die = 1;
     }
 
-    if ( $Foswiki::cfg{SMTP}{Debug} ) {
+    if ( $cfgData->{SMTP}{Debug} ) {
         _throwMsg( $level, $msg ) if ($die);
         chomp $msg;
         $msg =~ s,\n,\n -- ,g;
@@ -374,7 +374,7 @@ sub _logMailError {
         $logger = $this->app->logger;
     }
     else {
-        $logger = $Foswiki::cfg{Log}{Implementation};
+        $logger = $cfgData->{Log}{Implementation};
         if ($logger) {
             eval "require $logger;";
             die "Can't load $logger: $!\n" if ($@);
@@ -462,7 +462,7 @@ sub _installMailHandler {
         }
     }
 
-    if ( !$handler && $Foswiki::cfg{MailProgram} ) {
+    if ( !$handler && $this->app->cfg->data->{MailProgram} ) {
         $handler = \&_sendEmailBySendmail;
 
 #_logMailError('debug', "Set EMAIL HANDLER to $this->{MAIL_METHOD} $Foswiki::cfg{MailProgram}" );
@@ -486,6 +486,7 @@ alternative mail handling method.
 
 sub setMailHandler {
     my ( $this, $fnref ) = @_;
+    ASSERT( $fnref, "Mail handler code ref must not be undef" ) if DEBUG;
     $this->mailHandler($fnref);
 }
 
@@ -507,7 +508,7 @@ sub sendEmail {
 
     #_logMailError('debug', "sendEmail Entered");
 
-    unless ( $Foswiki::cfg{EnableEmail} ) {
+    unless ( $this->app->cfg->data->{EnableEmail} ) {
         return 'Cannot send mail: Foswiki email is disabled';
     }
 
@@ -614,14 +615,16 @@ sub _slurpFile( $$ ) {
 sub _smimeSignMessage {
     my $this = shift;
 
+    my $cfgData = $this->app->cfg->data;
+
     my ( $certFile, $keyFile ) = (
-        $Foswiki::cfg{Email}{SmimeCertificateFile},
-        $Foswiki::cfg{Email}{SmimeKeyFile}
+        $cfgData->{Email}{SmimeCertificateFile},
+        $cfgData->{Email}{SmimeKeyFile}
     );
     unless ( $certFile && $keyFile ) {
         ( $certFile, $keyFile ) = (
-            "$Foswiki::cfg{DataDir}/SmimeCertificate.pem",
-            "$Foswiki::cfg{DataDir}/SmimePrivateKey.pem"
+            $cfgData->{DataDir} . "/SmimeCertificate.pem",
+            $cfgData->{DataDir} . "/SmimePrivateKey.pem"
         );
 
         unless ( $certFile && $keyFile && -r $certFile && -r $keyFile ) {
@@ -645,8 +648,8 @@ sub _smimeSignMessage {
 
     # Decrypt key if password specified and file has encryption header.
 
-    if (   exists $Foswiki::cfg{Email}{SmimeKeyPassword}
-        && length $Foswiki::cfg{Email}{SmimeKeyPassword}
+    if (   exists $cfgData->{Email}{SmimeKeyPassword}
+        && length $cfgData->{Email}{SmimeKeyPassword}
         && $key =~ m/^-----BEGIN RSA PRIVATE KEY-----\n(?:(.*?\n)\n)?/s )
     {
         my %h;
@@ -670,12 +673,12 @@ sub _smimeSignMessage {
 #>>>
             $key = $pem->decode(
                 Content  => $key,
-                Password => $Foswiki::cfg{Email}{SmimeKeyPassword}
+                Password => $cfgData->{Email}{SmimeKeyPassword}
             );
             unless ($key) {
                 $this->_logMailError( 'die',
                         "Unable to decrypt "
-                      . $Foswiki::cfg{Email}{SmimeKeyFile} . ": "
+                      . $cfgData->{Email}{SmimeKeyFile} . ": "
                       . $pem->errstr
                       . ".  Mail will not be sent." );
                 return;
@@ -731,10 +734,12 @@ sub _fixEmail {
     require POSIX;
     POSIX->import(qw(locale_h));
 
+    my $cfgData = $this->app->cfg->data;
+
     my $old_locale = POSIX::setlocale( LC_TIME() );
     POSIX::setlocale( LC_TIME(), 'C' );
     my $dateStr;
-    if ( $Foswiki::cfg{Email}{Servertime} ) {
+    if ( $cfgData->{Email}{Servertime} ) {
         $dateStr = POSIX::strftime( '%a, %d %b %Y %T %z', localtime(time) );
     }
     else {
@@ -749,7 +754,7 @@ sub _fixEmail {
         $email->header_str_set( $header, $email->header($header) );
     }
 
-    if ( $Foswiki::cfg{Email}{EnableSMIME} ) {
+    if ( $cfgData->{Email}{EnableSMIME} ) {
 
         # TODO That would be much better to teach _smimeSignMessage to work
         # with pre-parsed email object. So far – this hack will do the job.
@@ -764,14 +769,16 @@ sub _fixEmail {
 sub _sendEmailBySendmail {
     my ( $this, $email ) = @_;
 
+    my $cfgData = $this->app->cfg->data;
+
     # With feedback, unsaved values are tainted.
     # We don't have special priveleges (or shouldn't), and
     # MailProgram allows specifying an arbitrary command - e.g. rm.
     # So there's not much point in trying to be defensive here.
 
-    my $mailer = $Foswiki::cfg{MailProgram} || '';
-    $mailer .= ' ' . ( $Foswiki::cfg{SMTP}{DebugFlags} || '' )
-      if ( $Foswiki::cfg{SMTP}{Debug} && $Foswiki::cfg{SMTP}{DebugFlags} );
+    my $mailer = $cfgData->{MailProgram} || '';
+    $mailer .= ' ' . ( $cfgData->{SMTP}{DebugFlags} || '' )
+      if ( $cfgData->{SMTP}{Debug} && $cfgData->{SMTP}{DebugFlags} );
     $mailer =~ m/^(.*)$/;
     $mailer = $1;
 
@@ -808,7 +815,9 @@ sub _sendEmailByNetSMTP {
     # XXX Check if our'ing of this has any impact on the functionality.
     my ( $this, $email ) = @_;
 
-    my $debug = $Foswiki::cfg{SMTP}{Debug} || 0;
+    my $cfgData = $this->app->cfg->data;
+
+    my $debug = $cfgData->{SMTP}{Debug} || 0;
 
     my $from = '';
     my @to   = ();
@@ -934,7 +943,7 @@ sub _sendEmailByNetSMTP {
     $smtp->startTLS( $this, $host ) if ($starttls);
 
     my ( $username, $password ) =
-      ( $Foswiki::cfg{SMTP}{Username}, $Foswiki::cfg{SMTP}{Password} );
+      ( $cfgData->{SMTP}{Username}, $cfgData->{SMTP}{Password} );
     $username = '' unless ( defined $username );
     $password = '' unless ( defined $password );
 
diff --git a/core/lib/Foswiki/Object.pm b/core/lib/Foswiki/Object.pm
index c8bfbe19d1..890ff72ac2 100644
--- a/core/lib/Foswiki/Object.pm
+++ b/core/lib/Foswiki/Object.pm
@@ -87,7 +87,7 @@ has __id => (
 has __clone_heap =>
   ( is => 'rw', clearer => 1, lazy => 1, default => sub { {} }, );
 
-around BUILDARGS {
+around BUILDARGS => sub {
     my $orig = shift;
     my ( $class, @params ) = @_;
 
@@ -101,6 +101,7 @@ around BUILDARGS {
 
     my $paramHash;
 
+    Carp::confess("Undefined \$class") unless defined $class;
     no strict 'refs';
     if ( defined *{ $class . '::_newParameters' }{ARRAY} ) {
         my @newParameters = @{ $class . '::_newParameters' };
diff --git a/core/lib/Foswiki/OopsException.pm b/core/lib/Foswiki/OopsException.pm
index a6bb47062a..0cf6baf157 100644
--- a/core/lib/Foswiki/OopsException.pm
+++ b/core/lib/Foswiki/OopsException.pm
@@ -154,6 +154,19 @@ around BUILDARGS => sub {
     my $orig  = shift;
     my $class = shift;
 
+    if ( ( @_ % 2 == 1 ) && ( scalar(@_) > 1 || ref( $_[0] ) ne 'HASH' ) ) {
+
+        # Add 'template' key to make arguments a valid key/value list.
+        # I.e. we suppose that the old calling format has been used with
+        # template name as the first positional argument.
+        # The old calling format also means that there is no `app' key. We
+        # add it manually. Sorry if won't always work as excepted, but
+        # there is no valid solution for this situation. `app' is added to
+        # the start of the list so that user provided key will override our
+        # default.
+        unshift @_, app => $Foswiki::app, 'template';
+    }
+
     my %params = @_;
 
     if ( defined $params{params} && !( ref( $params{params} ) eq 'ARRAY' ) ) {
@@ -176,19 +189,6 @@ sub BUILD {
     $this->_set_text( $this->stringify );
 }
 
-around BUILDARGS => sub {
-    my $orig  = shift;
-    my $class = shift;
-
-    # Check if we have received a valid key/value pair parameters including
-    # template => 'tmpl'.
-    if ( ( @_ % 2 == 1 ) && ( scalar(@_) > 1 || ref( $_[0] ) ne 'HASH' ) ) {
-        my $template = shift;
-        return $orig->( $class, template => $template, @_ );
-    }
-    return $orig->( $class, @_ );
-};
-
 =begin TML
 
 ---++ ObjectMethod stringify( [$wihtTemplate] ) -> $string
diff --git a/core/lib/Foswiki/PageCache.pm b/core/lib/Foswiki/PageCache.pm
index b58d8aa7e2..03cf2f30af 100644
--- a/core/lib/Foswiki/PageCache.pm
+++ b/core/lib/Foswiki/PageCache.pm
@@ -696,6 +696,14 @@ sub _handleDirtyArea {
         $prefs->popTopicContext();
     };
 
+    my $request = $app->request;
+    my $context = $request->url( -full => 1, -path => 1, -query => 1 ) . time();
+    my $cgis    = $app->users->getCGISession;
+    my $usingStrikeOne = $Foswiki::cfg{Validation}{Method} eq 'strikeone';
+
+    $text =~
+s/<input type='hidden' name='validation_key' value='(\?.*?)' \/>/Foswiki::Validation::updateValidationKey($cgis, $context, $usingStrikeOne, $1)/gei;
+
     #Foswiki::Func::writeDebug("out text='$text'") if TRACE;
     return $text;
 }
diff --git a/core/lib/Foswiki/Response.pm b/core/lib/Foswiki/Response.pm
index ea0e9f4a9a..2d9152b063 100644
--- a/core/lib/Foswiki/Response.pm
+++ b/core/lib/Foswiki/Response.pm
@@ -15,15 +15,13 @@ Fields:
 =cut
 
 package Foswiki::Response;
-use v5.14;
-use Assert;
 
+use Assert;
 use CGI::Util ();
+use Carp      ();
 
-use Moo;
-use namespace::clean;
+use Foswiki::Class qw(app);
 extends qw(Foswiki::Object);
-with qw(Foswiki::AppObject);
 
 BEGIN {
     if ( $Foswiki::cfg{UseLocale} ) {
@@ -75,7 +73,15 @@ cannot be changed (though the body can be modified)
 
 =cut
 
-has outputHasStarted => ( is => 'rw', lazy => 1, default => 0, );
+has _outputStartedAt => ( is => 'rw', lazy => 1, default => '', );
+has outputHasStarted => (
+    is      => 'rw',
+    lazy    => 1,
+    default => 0,
+    trigger => sub {
+        $_[0]->_outputStartedAt( Carp::longmess('') ) if DEBUG;
+    },
+);
 
 =begin TML
 
@@ -105,8 +111,7 @@ has status => (
     is      => 'rw',
     default => 200,
     trigger => sub {
-        ASSERT( !$_[0]->outputHasStarted, 'Too late to change status' )
-          if DEBUG;
+        $_[0]->_checkStartedOutput('Too late to change status');
     },
     coerce => sub {
         $_[0] =~ m/^(\d{3})/ ? int($1) : undef;
@@ -118,8 +123,7 @@ has headers => (
     default => sub { {} },
     trigger => sub {
         my $this = shift;
-        ASSERT( !$this->outputHasStarted, 'Too late to change headers' )
-          if DEBUG;
+        $this->_checkStartedOutput('Too late to change headers');
         my $headers = $this->headers;
         if ( defined $headers->{'Set-Cookie'} ) {
             my @cookies =
@@ -169,7 +173,7 @@ sub header {
     my ( $this, @p ) = @_;
     my (@header);
 
-    ASSERT( !$this->outputHasStarted, 'Too late to change headers' ) if DEBUG;
+    $this->_checkStartedOutput('Too late to change headers');
 
     # Ugly hack to avoid html escape in CGI::Util::rearrange
     local $CGI::Q = { escape => 0 };
@@ -390,7 +394,7 @@ Deletes headers whose names are passed.
 sub deleteHeader {
     my $this = shift;
 
-    ASSERT( !$this->outputHasStarted, 'Too late to change headers' ) if DEBUG;
+    $this->_checkStartedOutput('Too late to change headers');
 
     foreach (@_) {
         ( my $hdr = $_ ) =~ s/(?:^|(?<=-))(.)([^-]*)/\u$1\L$2\E/g;
@@ -409,7 +413,7 @@ Adds $value to list of values associated with header $name.
 sub pushHeader {
     my ( $this, $hdr, $value ) = @_;
 
-    ASSERT( !$this->outputHasStarted, 'Too late to change headers' ) if DEBUG;
+    $this->_checkStartedOutput('Too late to change headers');
 
     $hdr =~ s/(?:^|(?<=-))(.)([^-]*)/\u$1\L$2\E/g;
     my $cur = $this->headers->{$hdr};
@@ -430,8 +434,7 @@ sub pushHeader {
 sub cookies {
     my $this = shift;
     if (@_) {
-        ASSERT( !$this->outputHasStarted, 'Too late to change cookies' )
-          if DEBUG;
+        $this->_checkStartedOutput('Too late to change cookies');
         $this->setCookies(@_) if @_;
     }
     return @{ $this->getCookies };
@@ -454,7 +457,7 @@ CGI Compatibility Note: It doesn't support -target or -nph
 
 sub redirect {
     my ( $this, @p ) = @_;
-    ASSERT( !$this->outputHasStarted, 'Too late to redirect' ) if DEBUG;
+    $this->_checkStartedOutput('Too late to redirect');
     my ( $url, $status, $cookies ) = CGI::Util::rearrange(
         [ [qw(LOCATION URL URI)], 'STATUS', [qw(COOKIE COOKIES)], ], @p );
 
@@ -573,6 +576,26 @@ sub as_array {
     return \@rc;
 }
 
+# See if output has already been started and fail in DEBUG mode.
+sub _checkStartedOutput {
+    my $this = shift;
+    my ($msg) = @_;
+
+    if (DEBUG) {
+        ASSERT(
+            !$this->outputHasStarted,
+            $msg
+              . (
+                $this->_outputStartedAt
+                ? "\n---<<<Output started "
+                  . $this->_outputStartedAt
+                  . ">>>---"
+                : ''
+              )
+        );
+    }
+}
+
 1;
 __END__
 Foswiki - The Free and Open Source Wiki, http://foswiki.org/
diff --git a/core/lib/Foswiki/UI/Configure.pm b/core/lib/Foswiki/UI/Configure.pm
index ebe9e9edc5..9fbca81575 100644
--- a/core/lib/Foswiki/UI/Configure.pm
+++ b/core/lib/Foswiki/UI/Configure.pm
@@ -13,8 +13,8 @@ use v5.14;
 
 use Assert;
 
-use Foswiki                  ();
-use Foswiki::Configure::Auth ();
+use Foswiki ();
+require Foswiki::Configure::Auth;
 
 use Moo;
 use namespace::clean;
diff --git a/core/lib/Foswiki/Users.pm b/core/lib/Foswiki/Users.pm
index eb9424748b..1beaa87745 100644
--- a/core/lib/Foswiki/Users.pm
+++ b/core/lib/Foswiki/Users.pm
@@ -60,10 +60,8 @@ to a user.
 use Foswiki::AggregateIterator ();
 use Foswiki::LoginManager      ();
 
-use Moo;
-use namespace::clean;
+use Foswiki::Class qw(app);
 extends qw(Foswiki::Object);
-with qw(Foswiki::AppObject);
 
 use Assert;
 
@@ -135,7 +133,7 @@ sub BUILD {
     my $app = $this->app;
 
     # making basemapping
-    my $implBaseUserMappingManager = $Foswiki::cfg{BaseUserMappingManager}
+    my $implBaseUserMappingManager = $app->cfg->data->{BaseUserMappingManager}
       || 'Foswiki::Users::BaseUserMapping';
     Foswiki::load_package($implBaseUserMappingManager);
 
@@ -143,7 +141,8 @@ sub BUILD {
     #Foswiki::Exception::Fatal->throw( text => $@ ) if $@;
     $this->basemapping( $this->create($implBaseUserMappingManager) );
 
-    my $implUserMappingManager = $Foswiki::cfg{UserMappingManager} || 'none';
+    my $implUserMappingManager = $app->cfg->data->{UserMappingManager}
+      || 'none';
     $implUserMappingManager = 'Foswiki::Users::TopicUserMapping'
       if ( $implUserMappingManager eq 'none' );
 
diff --git a/core/lib/Foswiki/Validation.pm b/core/lib/Foswiki/Validation.pm
index b3d4da0dae..fd835fa373 100644
--- a/core/lib/Foswiki/Validation.pm
+++ b/core/lib/Foswiki/Validation.pm
@@ -92,6 +92,15 @@ sub addValidationKey {
     return "<input type='hidden' name='validation_key' value='?$nonce' />";
 }
 
+sub updateValidationKey {
+    my ( $cgis, $context, $strikeone, $oldKey ) = @_;
+
+    # expire old key
+    expireValidationKeys( $cgis, $oldKey );
+
+    return addValidationKey( $cgis, $context, $strikeone );
+}
+
 =begin TML
 
 ---++ StaticMethod generateValidationKey( $cgis, $context, $strikeone ) -> $nonce
diff --git a/core/tools/configure b/core/tools/configure
index 5584f0f811..638d8a3052 100755
--- a/core/tools/configure
+++ b/core/tools/configure
@@ -31,6 +31,7 @@ use Getopt::Long;
 use Storable qw(dclone);
 use Pod::Usage   ();
 use Data::Dumper ();
+use Try::Tiny;
 
 # Assume we are in the tools dir, and we can find bin and lib from there
 use FindBin;
@@ -46,7 +47,8 @@ use Assert;
 
 use Foswiki;
 use Foswiki::App;
-use Foswiki::Configure::Query;
+use Foswiki::Exception;
+require Foswiki::Configure::Query;
 
 {
 
@@ -97,7 +99,7 @@ use Foswiki::Configure::Query;
         $orig->( $this, $k );
 
         print Encode::encode_utf8(
-            "\$Foswiki::cfg$k = " . $this->changes->{$k} . ";\n");
+            "\$Foswiki::cfg$k = " . $this->changes->{$k} . ";\n" );
     };
 
     around WIZARD => sub {
@@ -258,7 +260,24 @@ sub _prompt {
 #$Foswiki::Configure::LoadSpec::RAW_VALS = 1;
 
 # Initialise
-my $app = Foswiki::App->new( env => dclone( \%ENV ), );
+
+$SIG{__DIE__} = sub {
+
+    # Somehow overriding of __DIE__ clashes with remote perl debugger in
+    # Komodo unless we die again instantly.
+    die $_[0] if (caller)[0] =~ /^DB::/;
+    Foswiki::Exception::Fatal->rethrow( $_[0] );
+};
+
+my $app;
+try {
+    $app = Foswiki::App->new( env => dclone( \%ENV ), );
+}
+catch {
+    my $e = $_;
+    say STDERR "App creation failed:", Foswiki::Exception::errorStr($e);
+    exit 1;
+};
 
 # Force config re-read to be independant of any possible variations in config
 # constructor.