Support testing commands and add first test

We have a lot of commands and it's important we test the ones that
are meant to be used in the future to ensure they work when they're
needed. Testing Flask commands is usually easy as written in their
docs [1], but I had to make some changes to the way we decorate the
command functions so they can work with test DB objects - I couldn't
find any example of someone else encountering the same problem.

[1]: https://flask.palletsprojects.com/en/2.0.x/testing/#testing-cli-commands

tests/app/test_commands.py

@@ -0,0 +1,26 @@
+import uuid
+
+from app.commands import local_dev_broadcast_permissions
+from app.dao.services_dao import dao_add_user_to_service
+from tests.app.db import create_user
+
+
+def test_local_dev_broadcast_permissions(
+    sample_service,
+    sample_broadcast_service,
+    notify_api,
+):
+    # create_user will pull existing unless email is unique
+    user = create_user(email=f'{uuid.uuid4()}@example.com')
+    dao_add_user_to_service(sample_service, user)
+    dao_add_user_to_service(sample_broadcast_service, user)
+
+    assert len(user.get_permissions(sample_service.id)) == 0
+    assert len(user.get_permissions(sample_broadcast_service.id)) == 0
+
+    notify_api.test_cli_runner().invoke(
+        local_dev_broadcast_permissions, ['-u', user.id]
+    )
+
+    assert len(user.get_permissions(sample_service.id)) == 0
+    assert len(user.get_permissions(sample_broadcast_service.id)) > 0