5.6Common Pitfalls

Forgetting constraints. Not all combinations are valid. SAML auth may only work with Enterprise accounts. If you do not model constraints, you get test cases that should never exist.

Confusing pairwise with random. Random sampling does not guarantee pair coverage. A random selection of 20 tests from 324 combinations will typically miss 30-40% of pairs.

Ignoring negative combinations. Pairwise covers valid interactions, but you also need tests for invalid combinations (e.g., negative quantity + expired coupon + missing auth).

Over-relying on AI optimality. AI-generated pairwise suites are good but not always mathematically minimal. For critical systems, verify with a dedicated tool.