functional tests: Make tests compatible with pytest-bdd v4.0

- In pytest-bdd v4.0, given steps are no longer fixtures. Mark steps
  as fixtures when needed.
- Remove 'test_' prefix from step function names, so that pytest doesn't
  run those twice.

Test performed:
- Run all tests, no more pytest-bdd v4.0 related failures
- All the openvpn, snapshot and users module tests pass

Signed-off-by: Veiko Aasa <veiko17@disroot.org>
Reviewed-by: Sunil Mohan Adapa <sunil@medhas.org>

plinth/modules/openvpn/tests/test_functional.py

@@ -13,7 +13,7 @@ base_url = functional.config['DEFAULT']['URL']
 shortcut_href = '?selected=shortcut-openvpn'
 
 
-@given('I download openvpn profile')
+@given('I download openvpn profile', target_fixture='openvpn_profile')
 def openvpn_download_profile(session_browser):
     return _download_profile(session_browser)
 
@@ -31,10 +31,9 @@ def openvpn_app_not_on_front_page(session_browser):
 
 
 @then('the openvpn profile downloaded should be same as before')
-def openvpn_profile_download_compare(session_browser,
-                                     openvpn_download_profile):
+def openvpn_profile_download_compare(session_browser, openvpn_profile):
     new_profile = _download_profile(session_browser)
-    assert openvpn_download_profile == new_profile
+    assert openvpn_profile == new_profile
 
 
 def _download_profile(browser):

plinth/modules/snapshot/tests/test_functional.py

@@ -18,7 +18,7 @@ def is_snapshots_supported(session_browser):
     assert True
 
 
-@given('the list of snapshots is empty')
+@given('the list of snapshots is empty', target_fixture='empty_snapshots_list')
 def empty_snapshots_list(session_browser):
     _delete_all(session_browser)
     return _get_count(session_browser)

plinth/modules/users/tests/test_functional.py

@@ -58,7 +58,7 @@ def new_user_does_not_exist(session_browser, name):
 
 
 @given(parsers.parse('the user {name:w} exists'))
-def test_user_exists(session_browser, name):
+def user_exists(session_browser, name):
     functional.nav_to_module(session_browser, 'users')
     user_link = session_browser.find_link_by_href(
         '/plinth/sys/users/{}/edit/'.format(name))
@@ -71,7 +71,7 @@ def test_user_exists(session_browser, name):
 
 @given(
     parsers.parse('the admin user {name:w} with password {password:w} exists'))
-def test_admin_user_exists(session_browser, name, password):
+def admin_user_exists(session_browser, name, password):
     functional.nav_to_module(session_browser, 'users')
     user_link = session_browser.find_link_by_href('/plinth/sys/users/' + name +
                                                   '/edit/')
@@ -82,7 +82,7 @@ def test_admin_user_exists(session_browser, name, password):
 
 
 @given(parsers.parse('the user {name:w} with password {password:w} exists'))
-def user_exists(session_browser, name, password):
+def user_exists_with_password(session_browser, name, password):
     functional.nav_to_module(session_browser, 'users')
     user_link = session_browser.find_link_by_href('/plinth/sys/users/' + name +
                                                   '/edit/')