Struct Selector

pub struct Selector {
    rng: TestRng,
    bias_increment: u64,
}

A value for picking random values out of iterators.

This is, in a sense, a more flexible variant of Index in that it can operate on arbitrary IntoIterator values.

Initially, the selection is roughly uniform, with a very slight bias towards items earlier in the iterator.

Shrinking causes the selection to move toward items earlier in the iterator, ultimately settling on the very first, but this currently happens in a very haphazard way that may fail to find the earliest failing input.

Example

Generate a non-indexable collection and a value to pick out of it.

use proptest::prelude::*;

proptest! {
    #[test]
    fn my_test(
        names in prop::collection::hash_set("[a-z]+", 10..20),
        selector in any::<prop::sample::Selector>()
    ) {
        println!("Selected name: {}", selector.select(&names));
        // Test stuff...
    }
}

Fields

rng: TestRng

bias_increment: u64

Implementations

impl Selector

pub fn select<T>(&self, it: T) -> <T as IntoIterator>::Item

where T: IntoIterator,

Pick a random element from iterable it.

The selection is unaffected by the elements themselves, and is dependent only on the actual length of it.

it is always iterated completely.

Panics

Panics if it has no elements.

pub fn try_select<T>(&self, it: T) -> Option<<T as IntoIterator>::Item>

where T: IntoIterator,

Pick a random element from iterable it.

Returns None if it is empty.

The selection is unaffected by the elements themselves, and is dependent only on the actual length of it.

it is always iterated completely.

Trait Implementations

impl Arbitrary for Selector

type Parameters = ()

The type of parameters that arbitrary_with accepts for configuration of the generated Strategy. Parameters must implement Default.

type Strategy = SelectorStrategy

The type of Strategy used to generate values of type Self.

fn arbitrary_with(_: ()) -> SelectorStrategy

Generates a Strategy for producing arbitrary values of type the implementing type (Self). The strategy is passed the arguments given in args.

fn arbitrary() -> Self::Strategy

Generates a Strategy for producing arbitrary values of type the implementing type (Self).

impl Clone for Selector

fn clone(&self) -> Selector

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Selector

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

Formats the value using the given formatter.