Ensure tests are actually run

pytest by default only discovers tests in files named test_*.py,
so none of the tests were actually being executed. Set the appropriate
pytest option
to discover the tests so they are automatically run.

tox.ini

@@ -34,10 +34,10 @@ deps =
 commands =
     pip install -e .
     pip install -e demo
-    # doctests
+    # doctests and unit tests
     pytest --cov=django_downloadview --cov=demoproject {posargs}
-    # all other test cases
-    coverage run --append {envbindir}/demo test {posargs: tests demoproject}
+    # demo project integration tests
+    coverage run --append {envbindir}/demo test {posargs: demoproject}
     coverage xml
     pip freeze
 ignore_outcome =
@@ -79,3 +79,4 @@ source = django_downloadview,demo
 [pytest]
 DJANGO_SETTINGS_MODULE = demoproject.settings
 addopts = --doctest-modules --ignore=docs/
+python_files = tests/*.py