Proptest

proptest is an open-source property-based testing framework for the Rust programming language. It enables tests to assert that certain properties hold for a wide range of automatically generated inputs rather than enumerating fixed cases. By exploring large input spaces, proptest helps reveal edge cases, and when a test fails, it automatically shrinks the counterexample to a minimal form to simplify debugging.

At the core of proptest are strategies, which describe how to generate data for tests. Tests can declare properties using the proptest! macro and compose complex inputs from simpler building blocks. Generated data can range from primitive values to collections or more complex, recursive structures. When a failure occurs, the framework applies shrinking rules to produce a smaller, still-failing input, aiding developers in pinpointing the root cause.

Key features include seamless integration with cargo test, a library of built-in strategies for common types, and facilities for composing custom strategies. Proptest supports customizing data generation, including user-defined types, and provides mechanisms to define or adjust shrinking behavior for specialized scenarios.

History and usage context indicate that proptest draws on the ideas of property-based testing popularized by QuickCheck in the Haskell community. It has evolved within the Rust ecosystem as a mature tool for testing invariants across diverse inputs. The project is distributed as a crate on crates.io and maintained on repositories such as GitHub, reflecting active adoption in Rust development workflows.

See also: QuickCheck, Hypothesis, property-based testing.