pytest Quick Start Guide

Checking warnings: pytest.warns

APIs also evolve. New and better alternatives to old functions are provided, arguments are removed, old ways of using a certain functionality evolve into better ways, and so on.

API writers have to strike a balance between keeping old code working to avoid breaking clients and providing better ways of doing things, while all the while keeping their own API code maintainable. For this reason, a solution often adopted is to start to issue warnings when API clients use the old behavior, in the hope that they update their code to the new constructs. Warning messages are shown in situations where the current usage is not wrong to warrant an exception, it just happens that there are new and better ways of doing ...