Add type annotations to tests

That was... a lot.

There are still errors in the os_sorted tests, but that requires me to
rethink some typing decisions in the main code so that will be for a
future commit.

1 files changed, 4 insertions, 1 deletions

diff --git a/tox.ini b/tox.ini
index fb2c58f..7bc66bc 100644
--- a/tox.ini
+++ b/tox.ini
@@ -56,8 +56,11 @@ skip_install = true
 [testenv:mypy]
 deps =
     mypy
+    hypothesis
+    pytest
+    pytest-mock
 commands =
-    mypy --strict natsort
+    mypy --strict natsort tests
 skip_install = true
 
 # Build documentation.