[TIP] Asserting side effects for an integration test

Doug Hellmann doug.hellmann at gmail.com
Thu Dec 24 08:16:27 PST 2009

On Dec 24, 2009, at 10:49 AM, Shawn Dahlen wrote:

> All,
> I'm looking for some advice on how to assert a side effect produced  
> by testing a function. Specifically, our project has a set of  
> command objects that internally use SQLAlchemy for database access.  
> We would like to have a set of integration tests that load a fixture  
> (using the Fixture project) into the database, execute the command,  
> and assert the results. For commands that return the result, this is  
> straightforward. However, we are debating how to assert commands  
> that create, update, or delete data.
> Option 1: In the test, call the CreateCommand then call the  
> GetItemsCommand asserting that the item count has increased. This  
> keeps our test unaware of the implementation detail but it breaks  
> isolation for testing the CreateCommand. My current thought is that  
> this would be ok since it is an integration test.
> Option 2: In the test, call the CreateCommand. Subsequently, use a  
> SQLAlchemy query in the test to assert the change in database state.  
> This would keep each test isolated, but it now exposes  
> implementation details.
> Your advice would be appreciated. Thanks.

I would go with option 1. Create it using your API, then query for the  
thing you created using your API to make sure it is there.


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