> only blow up when you execute one particular branch at runtime
On a related note: I'm a big fan of property-based testing, where each test is basically a function 'args => boolean', and we're asserting that it always returns true regardless of the given arguments (in reality there is usually more structure, for nicer error messages, skipping known edge cases, etc.). The test framework (e.g. Hypothesis, Quickcheck, Scalacheck, etc.) will run these functions on many different values, usually generated at random.
This works really well for 'algorithmic' code, e.g. '(x: Foo) => parse(print(x)) == x', but it can sometimes be difficult to think of general statements we can make about more complicated systems. In that case, it's often useful to test "code FOO returns without error". This is essentially fuzzing, and can be useful to find such problematic branches (at least, the "obvious", low-hanging fruit cases).
On a related note: I'm a big fan of property-based testing, where each test is basically a function 'args => boolean', and we're asserting that it always returns true regardless of the given arguments (in reality there is usually more structure, for nicer error messages, skipping known edge cases, etc.). The test framework (e.g. Hypothesis, Quickcheck, Scalacheck, etc.) will run these functions on many different values, usually generated at random.
This works really well for 'algorithmic' code, e.g. '(x: Foo) => parse(print(x)) == x', but it can sometimes be difficult to think of general statements we can make about more complicated systems. In that case, it's often useful to test "code FOO returns without error". This is essentially fuzzing, and can be useful to find such problematic branches (at least, the "obvious", low-hanging fruit cases).