When you say I 'forgot' an assertion, are you implying that test should include all possible assertions on the code? That would perhaps cover more surface, but

When you say I 'forgot' an assertion, are you implying that test should include all possible assertions on the code? That would perhaps cover more surface, but my goal (read zealot ideology) here is to have the tests help document the code: test "pressing d key makes mario move 2 pixels right" { expect { keyboard.d() }.to change { mario.x }.by(2) } I could test the value of the d() function, but I dont because I don't care what it returns. Didnt understand the "whole story invocation" and exception part, am I missing some context? Sure property-based testing can be invaluable in many situations. Only downside is if the tests become so complex to reason about that bugs become more likely in the tests than the implemenation. I've sometimes made tests with a manual list of inputs and a list of expected outputs for each. I'd still call that 1 assertion tests (just run multiple times), so my definition of 1 assertion might too broad..