com.pholser.junit.quickcheck.generator

Interface Gen<T>

Type Parameters:

T - type of values generated

All Known Implementing Classes:

ArrayGenerator, ComponentizedGenerator, CompositeGenerator, Ctor, EnumGenerator, ExhaustiveDomainGenerator, Fields, Generator, GuaranteeValuesGenerator, LambdaGenerator, SamplingDomainGenerator, ZilchGenerator

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface Gen<T>

Represents a strategy for generating random values.

Method Summary

Modifier and Type	Method and Description
default T	_gen(SourceOfRandomness random, GenerationStatus status) Deprecated. For use by junit-quickcheck only -- when we migrate to Java 9, this method will likely become private.
default Gen<T>	filter(Predicate<? super T> condition) Gives a generation strategy that produces a random value by having this strategy produce random values until one satisfies the given condition, then using that value as the result.
default Gen<Optional<T>>	filterOptional(Predicate<? super T> condition) Gives a generation strategy that produces a random value by having this strategy produce a random value and wrapping it in an Optional; if the value meets the given condition, the wrapping optional will be present.
default <U> Gen<U>	flatMap(Function<? super T,? extends Gen<? extends U>> mapper) Gives a generation strategy that produces a random value by having this strategy produce a random value, then applying the given function to that value, and asking the result to produce a value.
static <U> Pair<Integer,Gen<? extends U>>	freq(int weight, Gen<? extends U> generator) Helper for making a weighted generator indicator for frequency(Pair, Pair[]).
static <U> Gen<U>	frequency(Pair<Integer,Gen<? extends U>> first, Pair<Integer,Gen<? extends U>>... rest) Gives a generation strategy that produces a random value by choosing one of the given generators at random with probability in proportion to their given weights, and having it generate a value.
T	generate(SourceOfRandomness random, GenerationStatus status) Generates a value, possibly influenced by a source of randomness and metadata about the generation.
default <U> Gen<U>	map(Function<? super T,? extends U> mapper) Gives a generation strategy that produces a random value by having this strategy produce a random value, then applying the given function to that value, and returning the result.
static <U> Gen<U>	oneOf(Gen<? extends U> first, Gen<? extends U>... rest) Gives a generation strategy that produces a random value by choosing one of the given generators at random with (approximately) equal probability, and having it generate a value.
static <U> Gen<U>	oneOf(U first, U... rest) Gives a generation strategy that produces a random value by choosing one of the given values at random with (approximately) equal probability.
static <U> Gen<U>	pure(U constant) Gives a generation strategy that produces the given value, always.
default Gen<List<T>>	times(int times)

Method Detail

generate

T generate(SourceOfRandomness random,
           GenerationStatus status)

Generates a value, possibly influenced by a source of randomness and metadata about the generation.

Parameters:

random - source of randomness to be used when generating the value

status - an object that can be used to influence the generated value. For example, generating lists can use the size method to generate lists with a given number of elements.

Returns:

the generated value

map

default <U> Gen<U> map(Function<? super T,? extends U> mapper)

Gives a generation strategy that produces a random value by having this strategy produce a random value, then applying the given function to that value, and returning the result.

Type Parameters:

U - type of values produced by the mapped generation strategy

Parameters:

mapper - function that converts receiver's random values to result's values

Returns:

a new generation strategy

flatMap

default <U> Gen<U> flatMap(Function<? super T,? extends Gen<? extends U>> mapper)

Gives a generation strategy that produces a random value by having this strategy produce a random value, then applying the given function to that value, and asking the result to produce a value.

Type Parameters:

U - type of values produced by the mapped generation strategy

Parameters:

mapper - function that converts receiver's random values to another kind of generation strategy

Returns:

a new generation strategy

filter

default Gen<T> filter(Predicate<? super T> condition)

Gives a generation strategy that produces a random value by having this strategy produce random values until one satisfies the given condition, then using that value as the result.

Parameters:

condition - a condition the generated value is to meet

Returns:

a new generation strategy

filterOptional

default Gen<Optional<T>> filterOptional(Predicate<? super T> condition)

Gives a generation strategy that produces a random value by having this strategy produce a random value and wrapping it in an Optional; if the value meets the given condition, the wrapping optional will be present.

If the value meets the condition but is null, the wrapping optional will not be considered present.

Parameters:

condition - a condition the generated value is to meet

Returns:

a new generation strategy

times

default Gen<List<T>> times(int times)

pure

static <U> Gen<U> pure(U constant)

Gives a generation strategy that produces the given value, always.

Type Parameters:

U - type of values produced by the resulting strategy

Parameters:

constant - the value to be returned by the resulting strategy

Returns:

a new generation strategy

oneOf

@SafeVarargs
static <U> Gen<U> oneOf(U first,
                                     U... rest)

Gives a generation strategy that produces a random value by choosing one of the given values at random with (approximately) equal probability.

Type Parameters:

U - type of values produced by the resulting strategy

Parameters:

first - first possible choice

rest - the other possible choices

Returns:

a new generation strategy

oneOf

@SafeVarargs
static <U> Gen<U> oneOf(Gen<? extends U> first,
                                     Gen<? extends U>... rest)

Gives a generation strategy that produces a random value by choosing one of the given generators at random with (approximately) equal probability, and having it generate a value.

Type Parameters:

U - type of values produced by the resulting strategy

Parameters:

first - first possible generator choice

rest - the other possible generator choices

Returns:

a new generation strategy

frequency

@SafeVarargs
static <U> Gen<U> frequency(Pair<Integer,Gen<? extends U>> first,
                                         Pair<Integer,Gen<? extends U>>... rest)

Gives a generation strategy that produces a random value by choosing one of the given generators at random with probability in proportion to their given weights, and having it generate a value.

Type Parameters:

U - type of values produced by the resulting strategy

Parameters:

first - first possible (weighted) generator choice

rest - the other possible (weighted) generator choices

Returns:

a new generation strategy

freq

static <U> Pair<Integer,Gen<? extends U>> freq(int weight,
                                               Gen<? extends U> generator)

Helper for making a weighted generator indicator for frequency(Pair, Pair[]).

Type Parameters:

U - type of values produced by the given generation strategy

Parameters:

weight - an integer weight

generator - a generator

Returns:

a weight-generator pair

_gen

@Deprecated
default T _gen(SourceOfRandomness random,
                           GenerationStatus status)

Deprecated. For use by junit-quickcheck only -- when we migrate to Java 9, this method will likely become private.

Parameters:

random - source of randomness to be used when generating the value

status - an object that can be used to influence the generated value. For example, generating lists can use the size method to generate lists with a given number of elements.

Returns:

the generated value