enable using pytest-django

docs/docs/testing.md

@@ -25,3 +25,42 @@ Ran 14 tests in 4.142s
 OK
 Destroying test database for alias 'default'...
 ```
+
+Optionally, `pytest` can be used after installing `pytest` and `pytest-django`
+(which e.g. allows to execute single test cases):
+
+```bash
+$ cd /path/to/jane/root
+$ cd src
+$ pytest
+==================== test session starts ==================================
+platform linux -- Python 3.4.4, pytest-3.0.5, py-1.4.31, pluggy-0.4.0
+Django settings: jane.settings (from ini file)
+rootdir: /home/megies/git/jane-master/src, inifile: pytest.ini
+plugins: django-3.1.2
+collected 53 items
+
+jane/documents/tests/test_documents.py ...
+jane/fdsnws/tests/test_dataselect_1.py ................
+jane/fdsnws/tests/test_station_1.py ................
+jane/jane/tests/test_code_formatting.py .
+jane/quakeml/tests/test_quakeml.py ............
+jane/stationxml/tests/test_stationxml.py .
+jane/waveforms/tests/test_core.py ...
+jane/waveforms/tests/test_management_commands.py .
+
+================= 53 passed in 33.48 seconds ==============================
+
+$ pytest -k test_radial_query_quakeml
+==================== test session starts ==================================
+platform linux -- Python 3.4.4, pytest-3.0.5, py-1.4.31, pluggy-0.4.0
+Django settings: jane.settings (from ini file)
+rootdir: /home/megies/git/jane-master/src, inifile: pytest.ini
+plugins: django-3.1.2
+collected 53 items
+
+jane/quakeml/tests/test_quakeml.py .
+
+==================== 52 tests deselected ==================================
+============ 1 passed, 52 deselected in 4.92 seconds ======================
+```

src/jane/local_settings.py.example

@@ -95,7 +95,9 @@ JANE_FDSN_STATIONXML_SOURCE = "Jane"
 
 
 # Change the settings for the test database here!
-if 'test' in sys.argv:
+# for pytest-django, this did not work for me:
+# https://stackoverflow.com/a/25188424
+if 'test' in sys.argv or "pytest" in sys.modules:
     DATABASES = {
         'default': {
             'ENGINE': 'django.contrib.gis.db.backends.postgis',

src/jane/settings.py

@@ -290,7 +290,9 @@ def show_toolbar(request):
 
 
 # speed up tests
-if 'test' in sys.argv:
+# for pytest-django, this did not work for me:
+# https://stackoverflow.com/a/25188424
+if 'test' in sys.argv or "pytest" in sys.modules:
     print("Using test settings ...")
     PASSWORD_HASHERS = (
         'django.contrib.auth.hashers.MD5PasswordHasher',

src/pytest.ini

@@ -0,0 +1,5 @@
+[pytest]
+DJANGO_SETTINGS_MODULE = jane.settings
+django_find_project = true
+# -- recommended but optional:
+python_files = test_*.py