diff --git a/tox.ini b/tox.ini
index 5aa6b38..07e3180 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
-envlist = py37,pep8
-minversion = 3.1.1
+envlist = py3,pep8
+minversion = 3.18.0
 skipsdist = True
 ignore_basepython_conflict = True
 
@@ -10,8 +10,7 @@
 setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = bash -c 'if [ ! -d ./.testrepository ] ; then testr init ; fi'
-           testr run {posargs}
+commands = stestr run --slowest {posargs}
 
 [testenv:pep8]
 setenv =