unittest vs Storybook

Free and open source

Free and open source

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

Storybook itself is free. Chromatic, the hosted visual-review service from the same team, is a separate paid product.

Everything, self-hosted

Everything, self-hosted

Widely used

Python Software Foundation · since 2001

Category standard

Chromatic / OSS community · since 2016

• 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.

• One artefact serves as documentation, visual baseline and interaction test.
• Design-system teams get a shared reference that designers can actually open.
• Rich addon ecosystem for accessibility, viewport and state manipulation.

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

• Meaningful configuration and maintenance overhead; a neglected Storybook rots fast.
• Build times on large component libraries get long.
• Stories drift from production usage unless discipline is enforced.

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

Teams maintaining a design system or a large shared component library.