Struct ValueGenerator

pub struct ValueGenerator { /* private fields */ }

Context for generating single values out of strategies.

Proptest is designed to be built around “value trees”, which represent a spectrum from complex values to simpler ones. But in some contexts, like benchmarking or generating corpuses, one just wants a single value. This is a convenience struct for that.

Implementations

impl ValueGenerator

pub fn new() -> Self

Creates a new value generator with the default RNG.

pub fn deterministic() -> Self

Creates a new value generator with a deterministic RNG.

This generator has a hardcoded seed, so its results are predictable across test runs. However, a new proptest version may change the seed.

pub fn from_seed(seed: impl Hash) -> Self

Creates a new value generator from the given seed.

This generator is typically used with a hardcoded seed that is keyed on the input data somehow. For example, for a test fixture it may be the name of the fixture.

pub fn partial_clone(&mut self) -> Self

Does a “partial clone” of the ValueGenerator, creating a new independent but deterministic RNG.

pub fn generate<S: Strategy>(&mut self, strategy: S) -> S::Value

Generates a single value for this strategy.

Panics if generating the new value fails. The only situation in which this can happen is if generating the value causes too many internal rejects.

Trait Implementations

impl Debug for ValueGenerator

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ValueGenerator

fn default() -> ValueGenerator

Returns the “default value” for a type.