Random testing techniques like fuzz testing and property-based testing use random inputs to discover bugs that manual test cases miss. These approaches are especially effective at finding edge cases and security vulnerabilities.
Fuzz Testing
Fuzz testing bombards your application with random, malformed, or unexpected inputs to find crashes, memory leaks, and security vulnerabilities. It's particularly effective for parsers, file handlers, and network protocols. Many security vulnerabilities are discovered through fuzzing—including buffer overflows and injection attacks.
Property-Based Testing
Property-based testing generates random inputs and verifies that certain properties always hold. Instead of testing specific cases, you define invariants (e.g., "sorting then reversing equals reverse-sorting") and let the framework find counterexamples. This catches edge cases you wouldn't think to test manually.
Reproducibility
Random testing needs reproducibility for debugging. Always log or seed your random generator so you can replay failing cases. When a random test finds a bug, capture the exact inputs that caused it. Many frameworks support "shrinking"—automatically finding minimal failing inputs from random discoveries.