Struct TestRng

pub struct TestRng { /* private fields */ }

Available on crate feature testing only.

A fast, seedable pseudorandom number generator for use in tests which prints the seed if the thread in which it is created panics.

Only one TestRng is permitted per thread.

Implementations

impl TestRng

pub fn new() -> Self

Constructs a new TestRng using a seed generated from the env var CL_TEST_SEED if set or from cryptographically secure random data if not.

Note that new() or default() should only be called once per test. If a test needs to spawn multiple threads each with their own TestRng, then use new() to create a single, master TestRng, then use it to create a seed per child thread. The child TestRngs can then be constructed in their own threads via from_seed().

Panics

Panics if a TestRng has already been created on this thread.

pub fn from_seed(seed: <Pcg64Mcg as SeedableRng>::Seed) -> Self

Constructs a new TestRng using seed. This should be used in cases where a test needs to spawn multiple threads each with their own TestRng. A single, master TestRng should be constructed before any child threads are spawned, and that one should be used to create seeds for the child threads’ TestRngs.

Panics

Panics if a TestRng has already been created on this thread.

pub fn random_string<R: SampleRange<usize>>( &mut self, length_range: R, ) -> String

Returns a random String of length within the range specified by length_range.

pub fn random_vec<R: SampleRange<usize>, T>( &mut self, length_range: R, ) -> Vec<T>

where Standard: Distribution<T>,

Returns a random Vec of length within the range specified by length_range.

pub fn create_child(&mut self) -> Self

Creates a child RNG.

The resulting RNG is seeded from self deterministically.

Trait Implementations

impl Debug for TestRng

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

Formats the value using the given formatter.

impl Default for TestRng

fn default() -> Self

Returns the “default value” for a type.

impl Display for TestRng

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

Formats the value using the given formatter.

impl Drop for TestRng

fn drop(&mut self)

Executes the destructor for this type.

impl RngCore for TestRng

fn next_u32(&mut self) -> u32

Return the next random u32.

fn next_u64(&mut self) -> u64

Return the next random u64.

fn fill_bytes(&mut self, dest: &mut [u8])

Fill dest with random data.

fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>

Fill dest entirely with random data.

impl SeedableRng for TestRng

type Seed = <Mcg128Xsl64 as SeedableRng>::Seed

Seed type, which is restricted to types mutably-dereferenceable as u8 arrays (we recommend [u8; N] for some N).

fn from_seed(seed: Self::Seed) -> Self

Create a new PRNG using the given seed.

fn seed_from_u64(state: u64) -> Self

Create a new PRNG using a u64 seed.

fn from_rng<R>(rng: R) -> Result<Self, Error>

where R: RngCore,

Create a new PRNG seeded from another Rng.

fn from_entropy() -> Self

Creates a new instance of the RNG seeded via getrandom.

impl CryptoRng for TestRng