Struct LazyJust

pub struct LazyJust<T, F>
where
    F: Fn() -> T,
{ /* private fields */ }

A Strategy which always produces a single value value and never simplifies. If T is Clone, you should use Just instead.

This is a generalization of Just and works by calling the provided Fn () -> T in .current() every time. This is not a very interesting strategy, but is required in cases where T is not Clone. It is also used in proptest_derive where we can’t assume that your type is Clone.

It is important that the function used be pure.

Implementations

impl<T, F> LazyJust<T, F>

where F: Fn() -> T,

pub fn new(function: F) -> LazyJust<T, F>

Constructs a LazyJust strategy given the function/closure that produces the value.

It is important that the function used be pure.

Trait Implementations

impl<T, F> Clone for LazyJust<T, F>

where F: Clone + Fn() -> T,

fn clone(&self) -> LazyJust<T, F>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T, F> Debug for LazyJust<T, F>

where F: Fn() -> T,

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

Formats the value using the given formatter.

impl<T, F> Strategy for LazyJust<T, F>

where T: Debug, F: Clone + Fn() -> T,

type Tree = LazyJust<T, F>

The value tree generated by this Strategy.

type Value = T

The type of value used by functions under test generated by this Strategy.

fn new_tree( &self, _: &mut TestRunner, ) -> Result<<LazyJust<T, F> as Strategy>::Tree, Reason>

Generate a new value tree from the given runner.

fn prop_map<O, F>(self, fun: F) -> Map<Self, F>

where O: Debug, F: Fn(Self::Value) -> O, Self: Sized,

Returns a strategy which produces values transformed by the function fun.

fn prop_map_into<O>(self) -> MapInto<Self, O>

where O: Debug, Self: Sized, Self::Value: Into<O>,

Returns a strategy which produces values of type O by transforming Self with Into<O>.

fn prop_perturb<O, F>(self, fun: F) -> Perturb<Self, F>

where O: Debug, F: Fn(Self::Value, TestRng) -> O, Self: Sized,

Returns a strategy which produces values transformed by the function fun, which is additionally given a random number generator.

fn prop_flat_map<S, F>(self, fun: F) -> Flatten<Map<Self, F>>

where S: Strategy, F: Fn(Self::Value) -> S, Self: Sized,

Maps values produced by this strategy into new strategies and picks values from those strategies.

fn prop_ind_flat_map<S, F>(self, fun: F) -> IndFlatten<Map<Self, F>>

where S: Strategy, F: Fn(Self::Value) -> S, Self: Sized,

Maps values produced by this strategy into new strategies and picks values from those strategies while considering the new strategies to be independent.

fn prop_ind_flat_map2<S, F>(self, fun: F) -> IndFlattenMap<Self, F>

where S: Strategy, F: Fn(Self::Value) -> S, Self: Sized,

Similar to prop_ind_flat_map(), but produces 2-tuples with the input generated from self in slot 0 and the derived strategy in slot 1.

fn prop_filter<R, F>(self, whence: R, fun: F) -> Filter<Self, F>

where R: Into<Reason>, F: Fn(&Self::Value) -> bool, Self: Sized,

Returns a strategy which only produces values accepted by fun.

fn prop_filter_map<F, O>( self, whence: impl Into<Reason>, fun: F, ) -> FilterMap<Self, F>

where F: Fn(Self::Value) -> Option<O>, O: Debug, Self: Sized,

Returns a strategy which only produces transformed values where fun returns Some(value) and rejects those where fun returns None.

fn prop_union(self, other: Self) -> Union<Self>

where Self: Sized,

Returns a strategy which picks uniformly from self and other.

fn prop_recursive<R, F>( self, depth: u32, desired_size: u32, expected_branch_size: u32, recurse: F, ) -> Recursive<Self::Value, F>

where R: Strategy<Value = Self::Value> + 'static, F: Fn(BoxedStrategy<Self::Value>) -> R, Self: Sized + 'static,

Generate a recursive structure with self items as leaves.

fn prop_shuffle(self) -> Shuffle<Self>

where Self: Sized, Self::Value: Shuffleable,

Shuffle the contents of the values produced by this strategy.

fn boxed(self) -> BoxedStrategy<Self::Value>

where Self: Sized + 'static,

Erases the type of this Strategy so it can be passed around as a simple trait object.

fn sboxed(self) -> SBoxedStrategy<Self::Value>

where Self: Sized + Send + Sync + 'static,

Erases the type of this Strategy so it can be passed around as a simple trait object.

fn no_shrink(self) -> NoShrink<Self>

where Self: Sized,

Wraps this strategy to prevent values from being subject to shrinking.

impl<T, F> ValueTree for LazyJust<T, F>

where T: Debug, F: Fn() -> T,

type Value = T

The type of the value produced by this ValueTree.

fn simplify(&mut self) -> bool

Attempts to simplify the current value. Notionally, this sets the “high” value to the current value, and the current value to a “halfway point” between high and low, rounding towards low.

fn complicate(&mut self) -> bool

Attempts to partially undo the last simplification. Notionally, this sets the “low” value to one plus the current value, and the current value to a “halfway point” between high and the new low, rounding towards low.

fn current(&self) -> <LazyJust<T, F> as ValueTree>::Value

Returns the current value.

impl<T, F> Copy for LazyJust<T, F>

where F: Copy + Fn() -> T,