Why are my tests so slow? JUnit vs Gradle vs IntelliJ

I took a test yesterday and it said that I have the reaction time of a 25 year old.
My super speedy brain must be the reason that I find it so irritating to sit and wait for tests to complete. My MacBook Air is apparently 5.5 times faster than its equivalent 10 years ago, but I’m pretty that sure building and running the tests on a medium sized project is much less instant than it was then.
Why are my tests so slow?
In this episode
00:00:27 Both the test runners are lying
00:01:36 We can profile a Gradle build
00:02:37 The IntelliJ runner isn't reporting build time
00:03:28 Instrumenting the whole build and run
00:06:00 Speeding up our Gradle build by skipping a task
00:09:21 Running slow tests first
00:12:44 It's still all a bit rubbish
There is a playlist of TDD Gilded Rose episodes - • Test Driven Gilded Ros...
and one for Gradle • Gradle
The codebase is available on GitHub github.com/dmc...
I get lots of questions about the test progress bar. It was written by the inimitable @dmitrykandalov. To use it install his Liveplugin (plugins.jetbra...) and then this gist gist.github.co...
If you are going to be at KotlinConf 2025, or even just in Copenhagen in May, then you should sign up for the workshop that Nat Pryce and I are running. It’s called Refactoring to Functional Kotlin, and will give you hands-on experience of taking legacy code and safely migrating it to a functional style. Places are limited, so buy now at kotlinconf.com...
If you like this video, you’ll probably like my book Java to Kotlin, A Refactoring Guidebook (java-to-kotlin.dev). It's about far more than just the syntax differences between the languages - it shows how to upgrade your thinking to a more functional style.

[@DmitryKandalov]

Thank you so much for digging into the test runners' measurements! I'm sure the built-in IntelliJ test runner for Java was way faster. I might dig out an old version of IntelliJ to have proper evidence of software degradation (although sadly it doesn't feel like anyone would really care).

[@PairingWithDuncan]

I couldn’t have done it without your help - a great collaboration. I don’t think most people care as much as I do, but it takes me 10 minutes a week just to remove the pauses while nothing happens in my videos!

[@dom-]

I really care about shorter feedback loops. It would be great to have all those tests run below 1s, even if it's just a psychological barrier.

[@PairingWithDuncan]

Absolutely. Once you’ve experienced TDD with really fast feedback you don’t want to go back.