When Test Coverage Isn't Enough

Robert Roskam made a point on social media about the inadequacy of test coverage. 100% test coverage is not enough. Here’s an example as to why in Python: def division(x, y): return x / y If you pass in 0 for y, it’ll raise an error. You have to know to test for the value specifically. Test coverage won’t save you here. With 100% line coverage or branch coverages, it won’t be found. That’s how 100% test coverage is not enough. So, if test coverage is not enough, what can we do here? Well...