diff --git a/tox.ini b/tox.ini
index 78ea67b..05d20e6 100644
--- a/tox.ini
+++ b/tox.ini
@@ -10,8 +10,11 @@
                   pip install -U {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
+   LANGUAGE=en_US
+   LC_ALL=en_US.UTF-8
+   TESTS_DIR=./trsync/tests/unit/
 deps = -r{toxinidir}/test-requirements.txt
-commands = python setup.py test --slowest --testr-args='{posargs}'
+commands = python setup.py test --slowest --testr-args='{posargs:trsync.tests.unit}'
 
 [testenv:common-constraints]
 install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
@@ -57,4 +60,4 @@
 show-source = True
 ignore = E123,E125
 builtins = _
-exclude=.venv,.git,.tox,dist,doc,*openstack/common*,*lib/python*,*egg,build
\ No newline at end of file
+exclude=.venv,.git,.tox,dist,doc,*openstack/common*,*lib/python*,*egg,build