Where traditional example-based tests check software using manually-specified input-output pairs, property-based tests exploit a general description of valid inputs and program behaviour to automatically search for falsifying examples. Given that Python has excellent property-based testing tools, such tests are often easier to work with and routinely find serious bugs that all other techniques have missed.

I present four categories of properties relevant to most scientific projects, demonstrate how each found real bugs in Numpy and Astropy, and propose that property-based testing should be adopted more widely across the SciPy ecosystem.

Keywords:methodssoftwarevalidationproperty-based testing