# Shared Fixtures **Domain:** Testing / Interoperability **Doc Type:** Contract Component **Maturity:** Core Design Principle **Related:** [[wiki/Portable Contract|Portable Contract]], [[wiki/Conformance Testing|Conformance Testing]], [[wiki/Cross-Runtime Capability Parity|Cross-Runtime Capability Parity]] --- ## Definition **Shared fixtures are canonical input, output, and error examples consumed by every implementation of a capability.** They turn historical edge cases and design decisions into executable compatibility checks. ## Project Context The fixture corpus for the writing platform should include ordinary text, Unicode, punctuation, protected Markdown regions, nested quote markup, passage extraction, slug collisions, orphan detection, legacy aliases, and known historical irregularities. ## Key Insight **A fixture is a decision preserved in a form that future implementations cannot casually reinterpret.** ## See Also [[wiki/Conformance Testing|Conformance Testing]], [[wiki/Input Rules|Input Rules]], [[wiki/Normalized Output|Normalized Output]], [[wiki/Technical Terms|Technical Terms]]