/
RandomGenerators.java
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/
RandomGenerators.java
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package net.jqwik.engine.properties.arbitraries.randomized;
import java.math.*;
import java.util.*;
import java.util.concurrent.atomic.*;
import java.util.function.*;
import net.jqwik.api.*;
import net.jqwik.engine.properties.*;
import net.jqwik.engine.properties.arbitraries.*;
import net.jqwik.engine.properties.shrinking.*;
public class RandomGenerators {
public static final int DEFAULT_COLLECTION_SIZE = 255;
public static <U> RandomGenerator<U> choose(List<U> values) {
if (values.size() == 0) {
return fail("empty set of values");
}
return random -> {
U value = chooseValue(values, random);
return new ChooseValueShrinkable<>(value, values);
};
}
private static <U> U chooseValue(List<U> values, Random random) {
int index = random.nextInt(values.size());
return values.get(index);
}
public static <U> RandomGenerator<U> choose(U[] values) {
return choose(Arrays.asList(values));
}
public static <T extends Enum<T>> RandomGenerator<T> choose(Class<T> enumClass) {
return choose(enumClass.getEnumConstants());
}
public static RandomGenerator<Character> choose(char[] characters) {
List<Character> validCharacters = new ArrayList<>(characters.length);
for (char character : characters) {
validCharacters.add(character);
}
return choose(validCharacters);
}
public static RandomGenerator<Character> chars(char min, char max) {
return integers(min, max).map(anInt -> ((char) (int) anInt));
}
public static RandomGenerator<Byte> bytes(byte min, byte max) {
return bigIntegers(
BigInteger.valueOf(min),
BigInteger.valueOf(max),
defaultShrinkingTargetCalculator(BigInteger.valueOf(min), BigInteger.valueOf(max))
).map(BigInteger::byteValueExact);
}
public static RandomGenerator<Short> shorts(short min, short max) {
return bigIntegers(
BigInteger.valueOf(min),
BigInteger.valueOf(max),
defaultShrinkingTargetCalculator(BigInteger.valueOf(min), BigInteger.valueOf(max))
).map(BigInteger::shortValueExact);
}
public static RandomGenerator<Integer> integers(int min, int max) {
return bigIntegers(
BigInteger.valueOf(min),
BigInteger.valueOf(max),
defaultShrinkingTargetCalculator(BigInteger.valueOf(min), BigInteger.valueOf(max))
).map(BigInteger::intValueExact);
}
public static RandomGenerator<Long> longs(long min, long max) {
BigInteger min1 = BigInteger.valueOf(min);
BigInteger max1 = BigInteger.valueOf(max);
return bigIntegers(min1, max1, defaultShrinkingTargetCalculator(min1, max1)).map(BigInteger::longValueExact);
}
public static RandomGenerator<BigInteger> bigIntegers(
BigInteger min,
BigInteger max,
Function<BigInteger, BigInteger> shrinkingTargetCalculator,
BigInteger... partitionPoints
) {
Range<BigInteger> range = Range.of(min, max);
return RandomIntegralGenerators.bigIntegers(range, partitionPoints, shrinkingTargetCalculator);
}
public static RandomGenerator<Double> doubles(double min, double max, int scale) {
return bigDecimals(
BigDecimal.valueOf(min),
BigDecimal.valueOf(max), scale,
defaultShrinkingTargetCalculator(BigDecimal.valueOf(min), BigDecimal.valueOf(max))
).map(BigDecimal::doubleValue);
}
public static RandomGenerator<Float> floats(float min, float max, int scale) {
return bigDecimals(
BigDecimal.valueOf(min),
BigDecimal.valueOf(max), scale,
defaultShrinkingTargetCalculator(BigDecimal.valueOf(min), BigDecimal.valueOf(max))
).map(BigDecimal::floatValue);
}
public static RandomGenerator<BigDecimal> bigDecimals(
BigDecimal min,
BigDecimal max,
int scale,
Function<BigDecimal, BigDecimal> shrinkingTargetCalculator,
BigDecimal... partitionPoints
) {
return RandomDecimalGenerators.bigDecimals(Range.of(min, max), scale, partitionPoints, shrinkingTargetCalculator);
}
public static <T> RandomGenerator<List<T>> list(RandomGenerator<T> elementGenerator, int minSize, int maxSize) {
int defaultCutoff = defaultCutoffSize(minSize, maxSize);
return list(elementGenerator, minSize, maxSize, defaultCutoff);
}
public static <T> RandomGenerator<List<T>> list(
RandomGenerator<T> elementGenerator, int minSize, int maxSize, int cutoffSize
) {
Function<List<Shrinkable<T>>, Shrinkable<List<T>>> createShrinkable = elements -> new ShrinkableList<>(elements, minSize);
return container(elementGenerator, createShrinkable, minSize, maxSize, cutoffSize);
}
public static <T> RandomGenerator<T> oneOf(List<RandomGenerator<T>> all) {
return choose(all).flatMap(Function.identity());
}
public static <T> RandomGenerator<List<T>> shuffle(List<T> values) {
return random -> {
List<T> clone = new ArrayList<>(values);
Collections.shuffle(clone, random);
return Shrinkable.unshrinkable(clone);
};
}
public static RandomGenerator<String> strings(
RandomGenerator<Character> elementGenerator, int minLength, int maxLength, int cutoffLength
) {
Function<List<Shrinkable<Character>>, Shrinkable<String>> createShrinkable = elements -> new ShrinkableString(elements, minLength);
return container(elementGenerator, createShrinkable, minLength, maxLength, cutoffLength);
}
public static RandomGenerator<String> strings(
RandomGenerator<Character> elementGenerator, int minLength, int maxLength
) {
int defaultCutoff = defaultCutoffSize(minLength, maxLength);
return strings(elementGenerator, minLength, maxLength, defaultCutoff);
}
private static int defaultCutoffSize(int minSize, int maxSize) {
int range = maxSize - minSize;
int offset = (int) Math.max(Math.round(Math.sqrt(100)), 10);
if (range <= offset)
return maxSize;
return Math.min(offset + minSize, maxSize);
}
private static <T, C> RandomGenerator<C> container(
RandomGenerator<T> elementGenerator, //
Function<List<Shrinkable<T>>, Shrinkable<C>> createShrinkable,//
int minSize, int maxSize, int cutoffSize
) {
Function<Random, Integer> sizeGenerator = sizeGenerator(minSize, maxSize, cutoffSize);
return new ContainerGenerator<>(elementGenerator, createShrinkable, sizeGenerator);
}
private static Function<Random, Integer> sizeGenerator(int minSize, int maxSize, int cutoffSize) {
if (cutoffSize >= maxSize)
return random -> randomSize(random, minSize, maxSize);
// Choose size below cutoffSize with probability of 0.9
return random -> {
if (random.nextDouble() > 0.1)
return randomSize(random, minSize, cutoffSize);
else
return randomSize(random, cutoffSize + 1, maxSize);
};
}
private static int randomSize(Random random, int minSize, int maxSize) {
int range = maxSize - minSize;
return random.nextInt(range + 1) + minSize;
}
public static <T> RandomGenerator<Set<T>> set(RandomGenerator<T> elementGenerator, int minSize, int maxSize) {
int defaultCutoffSize = defaultCutoffSize(minSize, maxSize);
return set(elementGenerator, minSize, maxSize, defaultCutoffSize);
}
public static <T> RandomGenerator<Set<T>> set(
RandomGenerator<T> elementGenerator, int minSize, int maxSize, int cutoffSize
) {
Function<Random, Integer> sizeGenerator = sizeGenerator(minSize, maxSize, cutoffSize);
return random -> {
int listSize = sizeGenerator.apply(random);
Set<Shrinkable<T>> elements = new HashSet<>();
Set<T> values = new HashSet<>();
MaxTriesLoop.loop(
() -> elements.size() < listSize,
ignore -> {
Shrinkable<T> next = elementGenerator.next(random);
if (values.contains(next.value())) {
return Tuple.of(false, ignore);
}
elements.add(next);
values.add(next.value());
return Tuple.of(false, ignore);
},
maxMisses -> {
String message = String.format(
"Generating values for set of size %s missed more than %s times.",
listSize, maxMisses
);
return new JqwikException(message);
}
);
return new ShrinkableSet<>(elements, minSize);
};
}
public static <T> RandomGenerator<T> chooseShrinkable(List<Shrinkable<T>> shrinkables) {
if (shrinkables.size() == 0) {
return fail("empty set of shrinkables");
}
return random -> chooseValue(shrinkables, random);
}
public static <T> RandomGenerator<T> samplesFromShrinkables(List<Shrinkable<T>> samples) {
AtomicInteger tryCount = new AtomicInteger(0);
return ignored -> {
if (tryCount.get() >= samples.size())
tryCount.set(0);
return samples.get(tryCount.getAndIncrement());
};
}
public static <T> RandomGenerator<T> samples(T[] samples) {
List<Shrinkable<T>> shrinkables = SampleShrinkable.listOf(samples);
return samplesFromShrinkables(shrinkables);
}
public static <T> RandomGenerator<T> frequency(List<Tuple.Tuple2<Integer, T>> frequencies) {
return new FrequencyGenerator<>(frequencies);
}
public static <T> RandomGenerator<T> withEdgeCases(RandomGenerator<T> self, int genSize, List<Shrinkable<T>> edgeCases) {
if (edgeCases.isEmpty()) {
return self;
}
int baseToEdgeCaseRatio =
Math.min(
Math.max(Math.round(genSize / 5), 1),
100 / edgeCases.size()
) + 1;
RandomGenerator<T> edgeCasesGenerator = RandomGenerators.chooseShrinkable(edgeCases);
return random -> {
if (random.nextInt(baseToEdgeCaseRatio) == 0) {
return edgeCasesGenerator.next(random);
} else {
return self.next(random);
}
};
}
public static <T> RandomGenerator<T> fail(String message) {
return ignored -> {
throw new JqwikException(message);
};
}
public static int defaultCutoffSize(int minSize, int maxSize, int genSize) {
int range = maxSize - minSize;
int offset = (int) Math.max(Math.round(Math.sqrt(genSize)), 10);
if (range <= offset)
return maxSize;
return Math.min(offset + minSize, maxSize);
}
public static Function<BigInteger, BigInteger> defaultShrinkingTargetCalculator(BigInteger min, BigInteger max) {
return value -> ShrinkableBigInteger.defaultShrinkingTarget(value, Range.of(min, max));
}
public static Function<BigDecimal, BigDecimal> defaultShrinkingTargetCalculator(BigDecimal min, BigDecimal max) {
return value -> ShrinkableBigDecimal.defaultShrinkingTarget(value, Range.of(min, max));
}
// TODO: This could be way more sophisticated
public static BigInteger[] calculateDefaultPartitionPoints(int genSize, BigInteger min, BigInteger max) {
int partitionPoint = Math.max(genSize / 2, 10);
BigInteger upperPartitionPoint = BigInteger.valueOf(partitionPoint).min(max);
BigInteger lowerPartitionPoint = BigInteger.valueOf(partitionPoint).negate().max(min);
return new BigInteger[]{lowerPartitionPoint, upperPartitionPoint};
}
public static BigDecimal[] calculateDefaultPartitionPoints(int genSize, BigDecimal min, BigDecimal max) {
BigInteger[] partitionPoints = calculateDefaultPartitionPoints(genSize, min.toBigInteger(), max.toBigInteger());
return Arrays.stream(partitionPoints)
.map(BigDecimal::new)
.toArray(BigDecimal[]::new);
}
}