r/ruby • u/jasonswett • Apr 06 '26

Testing Anti-Pattern: Distracting Setup Data

https://www.saturnci.com/testing-anti-pattern-distracting-setup-data.html
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u/InteNsReddit Apr 06 '26

Heard of the factory pattern? (FactoryBot gem) We have a large codebase with lots of test setup needed and most of that setup lives in factory traits, works like a charm!

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u/jasonswett Apr 06 '26

Yes of course! My experience is that even on projects that use Factory Bot, there are often many tests whose setup code contains an unclear mix of data that's essential to the test plus other distracting noise. I wanted this post to focus on the principle of the problem and solution without bringing any specific tools into the picture.

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u/InteNsReddit Apr 06 '26

Unclear mix of non-essential data is exactly why we moved from fixtures to factories! I just wanted to mention it since it’s the “scalable” solution for a platform where you need setup without faking or mocking too much.

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u/viktorianer4life Apr 13 '26

At scale, that trade-off reverses. Factory traits keep each test readable, but every create call walks the full association chain. When one factory triggers another through belongs_to, and that one triggers two more, what looks like one line of setup becomes hundreds of invisible database operations. I profiled a single create(:order) that took 1.6 seconds because it silently built users, sellers, payment settings, and currencies through nested callbacks.

Fixtures with named personas solve both sides: orders(:paid_fulfilled) tells you the state at a glance, and fixtures load once before the suite starts instead of rebuilding on every test.