Document about the ways to write unit tests for Bolt apps

[offbyone]

I am looking to write unit tests for my Bolt API, which consists of an app with several handlers for events / messages. The handlers are both decorated using the app.event decorator, and make use of the app object to access things like the db connection that has been put on it. For example:

# in main.py
app = App(
    token=APP_TOKEN,
    signing_secret=SIGNING_SECRET,
    process_before_response=True,
    token_verification_enabled=token_verification_enabled,
)
app.db = db

# in api.py:
from .main import app

@app.command("/slashcommand")
def slash_command(ack, respond):
    ack()
    results = app.db.do_query()
    respond(...)

The thing is, I cannot find any framework pointers, or documentation, on how I would write reasonable unit tests for this. Presumably ones where the kwargs like ack and respond are replaced by test doubles. How do I do this?

The page URLs

• https://slack.dev/bolt-python/

Requirements

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[seratch]

Hi @offbyone, thanks for taking the time to write in!

As we have been receiving feedback about testing, it's on our radar. I cannot tell when we can release built-in test support but I myself will be working on it in the latter half of this year.

At this moment, the only thing I can suggest is to do something similar with the tests this project has. You can find so many tests under this package: https://github.com/slackapi/bolt-python/tree/v1.6.1/tests/scenario_tests

The key points are:

• Have your own mock server like this, which responds to Web API calls / response_url calls from test code. You don't need to use the standard HTTP server module for it.
• App instances in tests need to have client argument in its constructor. The client's base_url needs to point the mock server's URL this way
• Prepare request payload example data like this

In addition to above,

I cannot find any framework pointers

You can use any testing frameworks (my recommendation is pytest). The forthcoming testing support won't require your tests to rely on a specific test framework. We may provde some additional utility for pytest etc. for convenience, though.

Presumably ones where the kwargs like ack and respond are replaced by test doubles. How do I do this?

For respond, you can have a local mock HTTP server for handling the request. Regarding the ack call, it will be eventually converted to either an HTTP response or WebSocket message (Socket Mode) but before that, you can verify the value by checking response: Response returned by App#dispatch method as this test does.

I know that this approach is not so easy but it should be reasonable enough. Please consider going with it for now.

I hope this was helpful to you. If everything is clear for now, would you mind closing this issue? For the testing support task, I will come up with a bit more detailed issue soon. Also, for better documentation, we will add the section for testing once we release built-in testing support.

[offbyone]

Yeah, it ... helps. I guess I'd consider, if I were you, leaving this issue open to track that there is a gap, and resolving it when that documentation exists. If you don't track issues that way, please feel free to close it, but as far as I'm concerned this is still a bug until I can go to your documentation site and see instructions on how to test my bot :D

[seratch]

if I were you, leaving this issue open to track that there is a gap, and resolving it when that documentation exists

Yeah, I understand this way. It's also fine to keep this open for now. I have a link to this in the new issue that organizes the tasks/discussions around testing support. Thanks for the nice suggestion.

[offbyone]

I have a further question: Since this kind of testing requires constructing the app object differently, but the object is created at the module level, does someone there have a working pattern for how to do this in the bot code itself? Your example tests all create the app in the tests, but in a real Bolt application by the time you've imported the code, the App already exists and has been configured. So it's really tricky trying to sort out the right method here.

[carlos-alberto]

Hey @seratch is there any update on when this will be released?

[seratch]

@carlos-alberto I did a quick prototyping late last year. After that, we haven't had good progress due to other priorities. But we're aiming to provide a better solution sometime this year!