diff --git a/t/05-scheduler-full.t b/t/05-scheduler-full.t
index c0cc9d42036..58e8f6cd91b 100644
--- a/t/05-scheduler-full.t
+++ b/t/05-scheduler-full.t
@@ -27,7 +27,7 @@ use OpenQA::Scheduler::Client;
 use OpenQA::Scheduler::Model::Jobs;
 use OpenQA::WebAPI;
 use OpenQA::Worker::WebUIConnection;
-use OpenQA::Utils;
+use OpenQA::Utils qw(service_port);
 require OpenQA::Test::Database;
 use OpenQA::Test::Utils qw(
   setup_mojo_app_with_default_worker_timeout
@@ -35,8 +35,9 @@ use OpenQA::Test::Utils qw(
   create_webapi setup_share_dir create_websocket_server
   stop_service unstable_worker
   unresponsive_worker broken_worker rejective_worker
-  wait_for simulate_load
+  wait_for simulate_load setup_random_base_port
 );
+setup_random_base_port;
 use OpenQA::Test::TimeLimit '150';
 
 # treat this test like the fullstack test
diff --git a/t/25-cache-service.t b/t/25-cache-service.t
index ad520c260c7..8d57fc7aad6 100644
--- a/t/25-cache-service.t
+++ b/t/25-cache-service.t
@@ -10,15 +10,20 @@ $ENV{MOJO_LOG_LEVEL} = 'info';
 my $tempdir;
 
 BEGIN {
-    use Mojo::File qw(path tempdir);
-
     $ENV{OPENQA_CACHE_SERVICE_QUIET} = $ENV{HARNESS_IS_VERBOSE} ? 0 : 1;
     $ENV{OPENQA_CACHE_ATTEMPTS} = 3;
     $ENV{OPENQA_CACHE_ATTEMPT_SLEEP_TIME} = 0;
     $ENV{OPENQA_RSYNC_RETRY_PERIOD} = 0;
     $ENV{OPENQA_RSYNC_RETRIES} = 1;
     $ENV{OPENQA_METRICS_DOWNLOAD_SIZE} = 1024;
-    $ENV{OPENQA_BASE_PORT} = 20000 + int rand 10000;
+}
+
+use OpenQA::Test::Utils
+  qw(fake_asset_server cache_minion_worker cache_worker_service wait_for_or_bail_out perform_minion_jobs wait_for setup_random_base_port);
+setup_random_base_port;
+
+BEGIN {
+    use Mojo::File qw(path tempdir);
     $ENV{OPENQA_TEST_WAIT_INTERVAL} = 0.05;
 
     $tempdir = tempdir;
@@ -47,7 +52,7 @@ use POSIX '_exit';
 use Mojo::IOLoop::ReadWriteProcess qw(queue process);
 use Mojo::IOLoop::ReadWriteProcess::Session 'session';
 use OpenQA::Test::Utils
-  qw(fake_asset_server cache_minion_worker cache_worker_service wait_for_or_bail_out perform_minion_jobs wait_for);
+  qw(fake_asset_server cache_minion_worker cache_worker_service wait_for_or_bail_out perform_minion_jobs wait_for setup_random_base_port);
 use OpenQA::Test::TimeLimit '90';
 use Mojo::Util qw(md5_sum);
 use OpenQA::CacheService;
diff --git a/t/33-developer_mode.t b/t/33-developer_mode.t
index 5afaa05454c..20fb82d1a21 100644
--- a/t/33-developer_mode.t
+++ b/t/33-developer_mode.t
@@ -34,8 +34,9 @@ use Module::Load::Conditional 'can_load';
 use OpenQA::Utils qw(service_port);
 use OpenQA::Test::Utils qw(
   create_websocket_server create_scheduler create_live_view_handler setup_share_dir setup_fullstack_temp_dir
-  start_worker stop_service
+  start_worker stop_service setup_random_base_port
 );
+setup_random_base_port;
 use OpenQA::Test::FullstackUtils;
 use OpenQA::SeleniumTest;
 
@@ -48,9 +49,13 @@ my $livehandler;
 my $scheduler;
 
 sub turn_down_stack {
-    stop_service($_) for ($worker, $ws, $livehandler, $scheduler);
+    stop_service $scheduler;
+    stop_service $livehandler;
+    stop_service $ws;
+    stop_service $worker;
 }
 
+
 driver_missing unless check_driver_modules;
 
 # setup directories
diff --git a/t/43-scheduling-and-worker-scalability.t b/t/43-scheduling-and-worker-scalability.t
index 15b8d404d2f..b471ba19d16 100644
--- a/t/43-scheduling-and-worker-scalability.t
+++ b/t/43-scheduling-and-worker-scalability.t
@@ -25,7 +25,8 @@ use OpenQA::Log qw(setup_log);
 use OpenQA::Test::Utils qw(
   setup_mojo_app_with_default_worker_timeout
   create_user_for_workers create_webapi create_websocket_server
-  stop_service setup_fullstack_temp_dir simulate_load);
+  stop_service setup_fullstack_temp_dir simulate_load setup_random_base_port);
+setup_random_base_port;
 use OpenQA::Test::TimeLimit '20';
 use OpenQA::Utils 'testcasedir';
 
@@ -35,6 +36,14 @@ BEGIN {
     $ENV{SCALABILITY_TEST_WITH_OFFLINE_WEBUI_HOST} //= 1;
 }
 
+use OpenQA::Test::Utils qw(
+  setup_mojo_app_with_default_worker_timeout
+  create_user_for_workers create_webapi create_websocket_server
+  stop_service setup_fullstack_temp_dir simulate_load setup_random_base_port);
+setup_random_base_port;
+use OpenQA::Test::TimeLimit '20';
+use OpenQA::Utils 'testcasedir';
+
 setup_mojo_app_with_default_worker_timeout;
 OpenQA::Setup::read_config(my $app = OpenQA::App->singleton);
 
diff --git a/t/full-stack.t b/t/full-stack.t
index 85c0f5de552..ccd086e65fb 100644
--- a/t/full-stack.t
+++ b/t/full-stack.t
@@ -49,9 +49,11 @@ use Module::Load::Conditional 'can_load';
 use OpenQA::Test::Utils
   qw(create_websocket_server create_live_view_handler setup_share_dir),
   qw(cache_minion_worker cache_worker_service setup_fullstack_temp_dir),
-  qw(start_worker stop_service wait_for_or_bail_out);
+  qw(start_worker stop_service wait_for_or_bail_out setup_random_base_port);
+setup_random_base_port;
 use OpenQA::Test::FullstackUtils;
 
+
 plan skip_all => 'set FULLSTACK=1 (be careful)' unless $ENV{FULLSTACK};
 
 my $worker;
diff --git a/t/lib/OpenQA/Test/Utils.pm b/t/lib/OpenQA/Test/Utils.pm
index 65bf478a148..7f0a4f77882 100644
--- a/t/lib/OpenQA/Test/Utils.pm
+++ b/t/lib/OpenQA/Test/Utils.pm
@@ -50,6 +50,7 @@ BEGIN {
 
 our (@EXPORT, @EXPORT_OK);
 @EXPORT_OK = qw(
+  setup_random_base_port
   setup_mojo_app_with_default_worker_timeout create_user_for_workers
   create_webapi create_websocket_server create_scheduler create_live_view_handler
   unresponsive_worker broken_worker rejective_worker setup_share_dir setup_fullstack_temp_dir run_gru_job
@@ -60,16 +61,9 @@ our (@EXPORT, @EXPORT_OK);
   simulate_load
 );
 
-# The function OpenQA::Utils::service_port method hardcodes ports in a
-# sequential range starting with OPENQA_BASE_PORT. This can cause problems
-# especially in repeated testing if any of the ports in that range is already
-# occupied. So we inject random, free ports for the services here.
-#
-# Potential point for later improvement: In
-# Mojo::IOLoop::Server::generate_port keep the sock object on the port and
-# reuse it in listen to prevent race condition
-#
-# Potentially this approach can also be used in production code.
+sub setup_random_base_port {
+    $ENV{OPENQA_BASE_PORT} ||= 20000 + int rand 10000;
+}
 
 sub setup_mojo_app_with_default_worker_timeout ($class = 'Mojolicious') {
     my $app = $class->new(config => {global => {worker_timeout => DEFAULT_WORKER_TIMEOUT}}, log => undef);