dbt-unit-testing VS SS-Unit

If you use dbt for transformations Dbt Unit Testing (https://github.com/EqualExperts/dbt-unit-testing) is getting some attention (https://www.thoughtworks.com/radar/languages-and-frameworks?blipid=202304042)

dbt-unit-testing

We use this and take an example-based tests approach for any non-trivial tables: https://github.com/EqualExperts/dbt-unit-testing

> How do you test some SQL logic in isolation?

I do this using sql

1. Extracting an 'ephemeral model' to different model file

2. Mock out this model in upstream model in unit tests https://github.com/EqualExperts/dbt-unit-testing

3. Write unit tests for this model.

This is not different than regular software development in a language like java.

I would argue its even better better because unit tests are always in tabular format and pretty easy to understand. Java unit tests on other hand are never read by devs in practice.

I haven't done it yet but there are some popular blogs as well as a DBT package someone created.

> I really don’t understand the communities obsession with unwieldy tools like DBT.

It lets me write test first sql transforms. I never thought TDD sql would be possible. My sql is so much more readable with common logic extracted into ephmeral models. I practice same method to write clear code to write sql, eg: too many mocks = refactor into separate model ( class) .

I think DBT made this possible with refs that can be swapped out with mocks. This is the awesome library I am using https://github.com/EqualExperts/dbt-unit-testing

Back in the mid-noughties I decided to see if I could write SQL in a test-first manner (i.e. TDD). This resulted in me writing a 100% T-SQL based unit testing framework for SQL Server [1] which we then used for the SQL back-end at an investment bank.

On the back on that professional use I wrote a blog post [2] explaining why you might choose to go down this route as it wasn't the way database was developed way back then (SQL wasn't developed in the same way as the other front-end and back-end code).

A few years later I gave a short 20-minute talk (videoed) to show what writing SQL using TDD looked like for me. It's hard to show all the kinds of tests we wrote in practice at the bank but the talk is intended to show how rapid the feedback loop can be using a standard DB query tool and two code windows - production code and tests.

Be kind, it was a long time ago and I'm sure the state of the art has improved a lot in the intervening years :o).

Chris Oldwood

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[1] SQL Server Unit: https://github.com/chrisoldwood/SS-Unit

[2] You Write Your SQL Unit Tests in SQL?: https://chrisoldwood.blogspot.com/2011/04/you-write-your-sql...

[3] Test-Driven SQL: https://www.youtube.com/watch?v=5-MWYKLM3r0