> But for example, when I write a particle system, how would I test that? Do I test all combinations of parameters and then compare them with images, which take

> But for example, when I write a particle system, how would I test that? Do I test all combinations of parameters and then compare them with images, which takes a million years? Look up pairwise-independent combinatorial testing: https://github.com/Microsoft/pict https://github.com/Microsoft/pict > But what if your "escape string" function has a bug that kicks in at exactly 15 characters? Equivalence classes: Analyze which groups of inputs all exercise the same codepath, and test each group once. Boundary value testing: Anywhere there's a boundary between two different types of behavior, test the boundary, one less than the boundary, and one more than the boundary.