This editorial was originally published on Nov 10, 2009. It is being re-run as Steve is on vacation.
I saw a question on the SQLServerCentral ASK site the other day asking about unit testing for T-SQL stored procedures. There weren't many responses, but they were interesting to me.
I wondered how many people bothered to test their stored procedures as a unit. It seems that the idea of test driven development, or even of comprehensive testing of SQL code isn't very mature. If a query runs and appears to return the data we want, do we bother to test for edge or unusual data conditions?
Or do we even know how to write those kinds of tests?
Testing your code as it's being written is a well known way to reduce your technical debt and ensure better code when it's released. It's also a way to lower the cost of maintaining your software over its lifetime. However it slows down development as well.
That' s not why most people don't test their code well. The big reason is that it's B-O-R-I-N-G.
But does it matter? Is there really an issue? After all most T-SQL queries are built to scale. If the data is correctly assembled into sets with a small set of data, it will work correctly on large sets of data. Maybe not efficiently, but it tends to work. So is unit testing of T-SQL code important?
My guess is that it is not all that important. At least not as important as performance tuning. If you have extra time to spend on a query, I think most DBAs would prefer to spend it on making the SQL more efficient, not more tested.
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