Hi I m trying to implement some unit tests I think I m doing

Question

Hi I m trying to implement some unit tests I think I m doing it correctly But when I have an exception in my unit test including from an assertion error I have a series of exceptions from sql alchemy sqllite that aren t directly related to my code I m wondering if I m doing something wrong ```During handling of the above exception another exception occurred Traceback most recent call last File Users phil code dagster venv lib python3 8 site packages sqlalchemy pool base py line 763 in finalize fairy fairy reset pool transaction was reset File Users phil code dagster venv lib python3 8 site packages sqlalchemy pool base py line 1038 in reset pool dialect do rollback self File Users phil code dagster venv lib python3 8 site packages sqlalchemy engine default py line 683 in do rollback dbapi connection rollback sqlite3 ProgrammingError Cannot operate on a closed database ``` Full error in thread

Phil Dreizen · Answer

```FAILED civitech dagster tests test usvf py test elections Exception FORCED ==================================================================== 1 failed 1 passed 4 warnings in 3 66s ==================================================================== Exception during reset or similar Traceback most recent call last File Users phil code dagster venv lib python3 8 site packages dagster core execution api py line 280 in ephemeral instance if missing yield ephemeral instance GeneratorExit During handling of the above exception another exception occurred Traceback most recent call last File Users phil code dagster venv lib python3 8 site packages sqlalchemy pool base py line 763 in finalize fairy fairy reset pool transaction was reset File Users phil code dagster venv lib python3 8 site packages sqlalchemy pool base py line 1038 in reset pool dialect do rollback self File Users phil code dagster venv lib python3 8 site packages sqlalchemy engine default py line 683 in do rollback dbapi connection rollback sqlite3 ProgrammingError Cannot operate on a closed database Exception during reset or similar Traceback most recent call last File Users phil code dagster venv lib python3 8 site packages dagster core execution api py line 280 in ephemeral instance if missing yield ephemeral instance GeneratorExit During handling of the above exception another exception occurred Traceback most recent call last File Users phil code dagster venv lib python3 8 site packages sqlalchemy pool base py line 763 in finalize fairy fairy reset pool transaction was reset File Users phil code dagster venv lib python3 8 site packages sqlalchemy pool base py line 1038 in reset pool dialect do rollback self File Users phil code dagster venv lib python3 8 site packages sqlalchemy engine default py line 683 in do rollback dbapi connection rollback sqlite3 ProgrammingError Cannot operate on a closed database ```

Phil Dreizen · Answer

My unit test basically looks like this ```def test asset mock api = mock Mock mock api get return value = expected = context = dagster build op context actual = asset context the api=mock api assert actual == expected```

Phil Dreizen · Answer

^ Is that the correct way to set up a unit test for an asset

daniel · Answer

Does the error go away if you do this instead ```with dagster build op context as context actual = asset context the api=mock api ```

Phil Dreizen · Answer

I just gave that a try I still get the error

daniel · Answer

OK next try as a workaround ```with DagsterInstance ephemeral as instance context = dagster build op context instance=instance actual = asset context the api=mock api ``` If that fixes it there may be an underlying resource cleanup issue with our asset invocation API that we can investigate

daniel · Answer

you ll need to from dagster import DagsterInstance for that code to work

Phil Dreizen · Answer

That worked Thank you

daniel · Answer

Great I ll see if this is a problem on our end that workaround likely should not be needed

daniel · Answer

having some trouble reproducing Does your asset reference context instance at all Any chance that is sharable

daniel · Answer

oh wait no i can reproduce nevermind

daniel · Answer

although weirdly i can only reproduce if the test fails

daniel · Answer

i e this reproduces but assert True does not ```from dagster import asset build op context asset def my asset context pass def test asset gt None print HELLO expected = context = build op context actual = my asset context assert False```

Phil Dreizen · Answer

Yes same here I only get the error if the assert fails or any exception in the test

daniel · Answer

ah I think I see the problem

daniel · Answer

Is the error failing the test Or just logspew

Phil Dreizen · Answer

I think it s just logspew mostly

daniel · Answer

Ah ok if it s just logspew then I see why that would happen The reason my workaround works is that it forces python to clean things up in the correct order that takes dependencies into account instead of in a random one

Phil Dreizen · Answer

Ah got it Part of the reason I brought it up was that I wasn t sure if I was making some kind of error in how I wrote the test