diff --git a/script/check_dirty b/script/check_dirty
new file mode 100755
index 0000000000000..94db657a542db
--- /dev/null
+++ b/script/check_dirty
@@ -0,0 +1,7 @@
+#!/bin/bash
+[[ -z $(git ls-files --others --exclude-standard) ]] && exit 0
+
+echo -e '\n***** ERROR\nTests are leaving files behind. Please update the tests to avoid writing any files:'
+git ls-files --others --exclude-standard
+echo
+exit 1
diff --git a/tox.ini b/tox.ini
index 60dacd5d8cb02..dcfb209ef3a9c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,6 +13,7 @@ whitelist_externals = /usr/bin/env
 install_command = /usr/bin/env LANG=C.UTF-8 pip install {opts} {packages}
 commands =
      pytest --timeout=9 --duration=10 {posargs}
+     {toxinidir}/script/check_dirty
 deps =
      -r{toxinidir}/requirements_test_all.txt
      -c{toxinidir}/homeassistant/package_constraints.txt
@@ -29,6 +30,7 @@ whitelist_externals = /usr/bin/env
 install_command = /usr/bin/env LANG=C.UTF-8 pip install {opts} {packages}
 commands =
      pytest --timeout=9 --duration=10 --cov --cov-report= {posargs}
+     {toxinidir}/script/check_dirty
 deps =
      -r{toxinidir}/requirements_test_all.txt
      -c{toxinidir}/homeassistant/package_constraints.txt