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

app/commands.py

@@ -94,17 +94,25 @@ class notify_command:
         self.name = name
 
     def __call__(self, func):
-        # we need to call the flask with_appcontext decorator to ensure the config is loaded, db connected etc etc.
-        # we also need to use functools.wraps to carry through the names and docstrings etc of the functions.
-        # Then we need to turn it into a click.Command - that's what command_group.add_command expects.
-        @click.command(name=self.name)
-        @functools.wraps(func)
-        @flask.cli.with_appcontext
+        decorators = [
+            click.command(name=self.name),  # turn it into a click.Command
+            functools.wraps(func)  # carry through function name, docstrings, etc.
+        ]
+
+        # in the test environment the app context is already provided and having
+        # another will lead to the test db connection being closed prematurely
+        if os.getenv('NOTIFY_ENVIRONMENT', '') != 'test':
+            # with_appcontext ensures the config is loaded, db connected, etc.
+            decorators.insert(0, flask.cli.with_appcontext)
+
         def wrapper(*args, **kwargs):
             return func(*args, **kwargs)
 
-        command_group.add_command(wrapper)
+        for decorator in decorators:
+            # this syntax is equivalent to e.g. "@flask.cli.with_appcontext"
+            wrapper = decorator(wrapper)
 
+        command_group.add_command(wrapper)
         return wrapper