Struct proptest::test_runner::TestRng

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pub struct TestRng { /* private fields */ }
Expand description

Proptest’s random number generator.

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impl TestRng

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pub fn from_seed(algorithm: RngAlgorithm, seed: &[u8]) -> Self

Create a new RNG with the given algorithm and seed.

Any RNG created with the same algorithm-seed pair will produce the same sequence of values on all systems and all supporting versions of proptest.

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Panics if seed is not an appropriate length for algorithm.

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pub fn bytes_used(&self) -> Vec<u8>

Dumps the bytes obtained from the RNG so far (only works if the RNG is set to Recorder).

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Panics if this RNG does not capture generated data.

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pub fn deterministic_rng(algorithm: RngAlgorithm) -> Self

Returns a TestRng with a particular hard-coded seed.

The seed value will always be the same for a particular version of Proptest and algorithm, but may change across releases.

This is useful for testing things like strategy implementations without risking getting “unlucky” RNGs which deviate from average behaviour enough to cause spurious failures. For example, a strategy for bool which is supposed to produce true 50% of the time might have a test which checks that the distribution is “close enough” to 50%. If every test run starts with a different RNG, occasionally there will be spurious test failures when the RNG happens to produce a very skewed distribution. Using this or TestRunner::deterministic() avoids such issues.

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impl Clone for TestRng

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fn clone(&self) -> TestRng

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for TestRng

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

Formats the value using the given formatter. Read more
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impl RngCore for TestRng

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fn next_u32(&mut self) -> u32

Return the next random u32. Read more
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fn next_u64(&mut self) -> u64

Return the next random u64. Read more
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fn fill_bytes(&mut self, dest: &mut [u8])

Fill dest with random data. Read more
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fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>

Fill dest entirely with random data. Read more

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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default unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<R> Rng for R
where R: RngCore + ?Sized,

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fn gen<T>(&mut self) -> T

Return a random value supporting the Standard distribution. Read more
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fn gen_range<T, R>(&mut self, range: R) -> T
where T: SampleUniform, R: SampleRange<T>,

Generate a random value in the given range. Read more
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fn sample<T, D>(&mut self, distr: D) -> T
where D: Distribution<T>,

Sample a new value, using the given distribution. Read more
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fn sample_iter<T, D>(self, distr: D) -> DistIter<D, Self, T>
where D: Distribution<T>, Self: Sized,

Create an iterator that generates values using the given distribution. Read more
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fn fill<T>(&mut self, dest: &mut T)
where T: Fill + ?Sized,

Fill any type implementing Fill with random data Read more
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fn try_fill<T>(&mut self, dest: &mut T) -> Result<(), Error>
where T: Fill + ?Sized,

Fill any type implementing Fill with random data Read more
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fn gen_bool(&mut self, p: f64) -> bool

Return a bool with a probability p of being true. Read more
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fn gen_ratio(&mut self, numerator: u32, denominator: u32) -> bool

Return a bool with a probability of numerator/denominator of being true. I.e. gen_ratio(2, 3) has chance of 2 in 3, or about 67%, of returning true. If numerator == denominator, then the returned value is guaranteed to be true. If numerator == 0, then the returned value is guaranteed to be false. Read more
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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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fn vzip(self) -> V