Invariant testing from Clarity

This article is part of the Pandora series of articles.

Pandora enables property-based testing, fuzzing, and invariant testing for smart contracts that run on the Stacks 2.x layer-1 blockchain. Pandora discovers and run tests written in Clarity and TypeScript.

Conceptual exploration of native Clarity testing - Pandora was a prototype that was never released.

UPDATE (August 7, 2025): Since then, Rendezvous has been released! Check out the documentation for production-ready Clarity testing. See SIP-031 testing for real-world usage examples.

Prototype Syntax

;; Hypothetical native Clarity testing syntax
(define-public (prop-never-negative)
  (let ((current (contract-call? .counter get-counter)))
    (asserts! (>= current 0) (err u1))
    (ok true)))

(define-public (invariant-counter-bounded)
  (let ((counter-val (contract-call? .counter get-counter)))
    (asserts! (<= counter-val u1000000) (err u4))
    (ok true)))

This prototype explored native Clarity semantics for property-based testing without marshaling overhead, leveraging the same language for both contracts and tests to eliminate context switching while maintaining type safety through shared primitives.

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Next: Heterogeneous test-suites.