Karva
A Python test framework, written in Rust.
Run familiar function-based tests with parallel workers, process isolation, and the tools a serious test suite needs built in.
Try it in an existing project
uv add --dev karvauv run karva test
Performance
Look at the measurements.
Performance depends on the suite. This benchmark separates collection from execution so the comparison stays visible instead of becoming a vague speed claim.
karva2.60s
pytest-xdist60.50s
pytest92.20s
Workload: approximately 250,000 tests · Machine: 14 cores · Benchmark project
Why Karva
Fast by design. Small on purpose.
Karva keeps discovery, scheduling, reporting, and coverage in a Rust process. Python workers focus on running tests.
Compatibility stops where pytest behavior would make suites harder to understand or maintain. The smaller surface is deliberate.
Read the project non-goalsUseful features belong in the runner.
Karva owns the complete test run, so common workflows work together without a stack of third-party plugins.