Singleton Pattern / Testability
Kind: tension
Record: tension:singleton-pattern-testability
Canonical: Schema
"singleton-pattern" (design-patterns-core layer) is traded against "Testability" (computation-core layer) — a principle cannot be scope-separated from a quality, metric, or cost it competes with; resolve by measuring "Testability" and choosing an explicit operating point.
Listed in Tensions, after Prototype Pattern / Copy Semantics and before Singleton Pattern / Dependency Injection.