Principlev1PR-502
Design validation tests to target the boundaries where…
Design validation tests to target the boundaries where your schema is most likely to break rather than the center where it is most likely to hold.
Why This Is a Principle
This is derived from Patterns Exist in Hierarchical Logical Levels (patterns exist in hierarchical levels, deeper structures generate surface events) and Abstraction Necessarily Discards Information (abstraction discards information). A schema is an abstraction that represents a pattern across multiple levels. Edge cases reveal which information was discarded during abstraction and where the pattern hierarchy breaks. This is prescriptive (where to direct testing effort) rather than descriptive, making it a principle. It's general enough to apply to any schema validation context.