unittest vs JUnit 5

Free and open source

Free and open source

Free and open source. You pay in engineering time and CI minutes.

Free and open source. You pay in engineering time and CI minutes.

Everything, self-hosted

Everything, self-hosted

Widely used

Python Software Foundation · since 2001

Category standard

JUnit Team · since 2017

• In the standard library — nothing to install or vet.
• unittest.mock is excellent and used almost universally in Python.
• Familiar to anyone coming from JUnit or NUnit.

• Universal support across IDEs, build tools and CI in the Java ecosystem.
• The extension model replaced JUnit 4's runners and rules with something composable.
• Pairs cleanly with Mockito, AssertJ, Spring Test and Testcontainers.

• Verbose compared to pytest for the same coverage.
• No parametrisation or fixture composition worth the name.
• Most teams run unittest tests through pytest anyway.

• Java verbosity persists — expect more lines per test than in Python or JavaScript.
• Parallel execution is opt-in and still occasionally surprising.
• Mixed JUnit 4 and 5 codebases need the vintage engine and stay confusing for years.

Standard-library-only environments and codebases that already use it.

Every Java and Kotlin project on the JVM.