Make test more robust

Now tests:
- that the user doesn’t have the usage menu item when they’re not a
  member of the organisation (i.e. the counterfactual)
- that the user still gets a 403 when they try to view the usage page if
  they’re not a member of the organisation

tests/app/main/test_permissions.py

@@ -378,7 +378,28 @@ def test_service_navigation_for_org_user(
     ]
 
 
-def test_org_user_who_is_also_service_user_can_still_see_usage_page(
+@pytest.mark.parametrize('user_organisations, expected_menu_items, expected_status', [
+    (
+        [],
+        (
+            'Templates',
+            'Sent messages',
+            'Team members',
+        ),
+        403,
+    ),
+    (
+        [ORGANISATION_ID],
+        (
+            'Templates',
+            'Sent messages',
+            'Team members',
+            'Usage',
+        ),
+        200,
+    ),
+])
+def test_service_user_without_manage_service_permission_can_see_usage_page_when_org_user(
     client_request,
     mocker,
     active_caseworking_user,
@@ -390,9 +411,14 @@ def test_org_user_who_is_also_service_user_can_still_see_usage_page(
     mock_get_invites_for_service,
     mock_get_users_by_service,
     mock_get_service_organisation,
+    mock_get_service_templates,
+    mock_get_template_folders,
+    user_organisations,
+    expected_status,
+    expected_menu_items,
 ):
     active_caseworking_user['services'] = [SERVICE_ONE_ID]
-    active_caseworking_user['organisations'] = [ORGANISATION_ID]
+    active_caseworking_user['organisations'] = user_organisations
     service = service_json(
         id_=SERVICE_ONE_ID,
         organisation_id=ORGANISATION_ID,
@@ -402,19 +428,19 @@ def test_org_user_who_is_also_service_user_can_still_see_usage_page(
         return_value={'data': service}
     )
     client_request.login(active_caseworking_user, service=service)
-
     page = client_request.get(
-        'main.usage',
+        'main.choose_template',
         service_id=SERVICE_ONE_ID,
     )
-    assert [
+    assert tuple(
         item.text.strip() for item in page.select('nav.navigation a')
-    ] == [
+    ) == expected_menu_items
-        'Templates',
+
-        'Sent messages',
+    client_request.get(
-        'Team members',
+        'main.usage',
-        'Usage',
+        service_id=SERVICE_ONE_ID,
-    ]
+        _expected_status=expected_status,
+    )
 
 
 def get_name_of_decorator_from_ast_node(node):