diff --git a/tox.ini b/tox.ini
index 268db1846..c20f4ffa1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -23,7 +23,7 @@ deps =
     -r{toxinidir}/test-requirements.txt
 commands =
     coverage erase
-    stestr run --serial --test-path {[testenv]unit_tests} {posargs}
+    stestr run --random --slowest --test-path {[testenv]unit_tests} {posargs}
 
 [testenv:pep8]
 allowlist_externals = flake8