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refactor: replace concrete DeterministicRandom with RandomSource interface
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‎fixture-monkey-api/src/main/java/com/navercorp/fixturemonkey/api/random/DeterministicRandom.java‎

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‎fixture-monkey-api/src/main/java/com/navercorp/fixturemonkey/api/random/DeterministicRandomSource.java‎

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/*
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* Fixture Monkey
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*
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* Copyright (c) 2021-present NAVER Corp.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.navercorp.fixturemonkey.api.random;
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import java.util.LinkedHashMap;
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import java.util.Map;
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import java.util.Random;
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import org.apiguardian.api.API;
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import org.apiguardian.api.API.Status;
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/**
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* A RandomSource implementation that caches random instances by seed values.
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* This enables deterministic random generation by reusing random instances for the same seed.
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* The cache is limited to a maximum of 32 entries to prevent memory leaks.
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*
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* @since 1.1.16
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*/
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@API(since = "1.1.16", status = Status.EXPERIMENTAL)
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public final class DeterministicRandomSource implements RandomSource {
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private static final int MAX_CACHE_SIZE = 32;
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private final Map<Long, Random> seedCache;
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private final Random baseRandom;
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private long currentSeed;
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/**
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* Creates a new DeterministicRandomSource with the given initial seed.
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*
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* @param initialSeed the initial seed value
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*/
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public DeterministicRandomSource(long initialSeed) {
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this.baseRandom = new Random(initialSeed);
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this.currentSeed = initialSeed;
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this.seedCache = new LinkedHashMap<Long, Random>(MAX_CACHE_SIZE, 0.75f, true) {
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@Override
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protected boolean removeEldestEntry(Map.Entry<Long, Random> eldest) {
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return size() > MAX_CACHE_SIZE;
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}
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};
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}
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@Override
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public long nextSeed() {
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long seed = this.baseRandom.nextLong();
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this.currentSeed = seed;
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this.seedCache.computeIfAbsent(seed, Random::new);
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return seed;
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}
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@Override
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public Random getRandom(long seed) {
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return this.seedCache.get(seed);
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}
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@Override
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public Random getCurrentSeedRandom() {
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return this.seedCache.get(this.currentSeed);
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}
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}

‎fixture-monkey-api/src/main/java/com/navercorp/fixturemonkey/api/random/RandomSource.java‎

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/*
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* Fixture Monkey
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*
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* Copyright (c) 2021-present NAVER Corp.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.navercorp.fixturemonkey.api.random;
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import java.util.Random;
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import org.apiguardian.api.API;
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import org.apiguardian.api.API.Status;
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/**
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* Provides random instances with seed management capabilities.
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* Implementations may cache random instances for deterministic behavior.
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*
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* @since 1.1.16
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*/
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@API(since = "1.1.16", status = Status.EXPERIMENTAL)
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public interface RandomSource {
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/**
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* Generates and returns the next seed value.
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* The implementation may cache a random instance associated with the returned seed.
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*
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* @return the next seed value
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*/
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long nextSeed();
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/**
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* Retrieves a random instance associated with the given seed.
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* Returns null if no random instance is associated with the seed.
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*
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* @param seed the seed value
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* @return the random instance associated with the seed, or null if not found
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*/
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Random getRandom(long seed);
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/**
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* Retrieves the random instance associated with the current seed.
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* The current seed is the last value returned by {@link #nextSeed()}.
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*
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* @return the random instance associated with the current seed, or null if not found
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*/
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Random getCurrentSeedRandom();
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}

‎fixture-monkey-api/src/test/java/com/navercorp/fixturemonkey/api/random/DeterministicRandomSourceTest.java‎

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/*
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* Fixture Monkey
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*
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* Copyright (c) 2021-present NAVER Corp.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.navercorp.fixturemonkey.api.random;
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import static org.assertj.core.api.BDDAssertions.then;
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import java.util.Random;
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import net.jqwik.api.ForAll;
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import net.jqwik.api.Property;
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import net.jqwik.api.constraints.LongRange;
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class DeterministicRandomSourceTest {
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@Property
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void nextSeedCachesRandomInstance(@ForAll @LongRange(min = 1L) long initialSeed) {
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// given
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RandomSource randomSource = new DeterministicRandomSource(initialSeed);
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// when
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long seed = randomSource.nextSeed();
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// then
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Random random = randomSource.getRandom(seed);
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then(random).isNotNull();
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}
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@Property
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void getRandomRetrievesCachedInstance(@ForAll @LongRange(min = 1L) long initialSeed) {
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// given
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RandomSource randomSource = new DeterministicRandomSource(initialSeed);
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long seed = randomSource.nextSeed();
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// when
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Random firstRetrieval = randomSource.getRandom(seed);
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Random secondRetrieval = randomSource.getRandom(seed);
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// then
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then(firstRetrieval).isNotNull();
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then(firstRetrieval).isSameAs(secondRetrieval);
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}
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@Property
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void getCurrentSeedRandomReturnsCurrentSeedRandom(@ForAll @LongRange(min = 1L) long initialSeed) {
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// given
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RandomSource randomSource = new DeterministicRandomSource(initialSeed);
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// when
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long firstSeed = randomSource.nextSeed();
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Random firstRandom = randomSource.getCurrentSeedRandom();
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long secondSeed = randomSource.nextSeed();
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Random secondRandom = randomSource.getCurrentSeedRandom();
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// then
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then(firstRandom).isSameAs(randomSource.getRandom(firstSeed));
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then(secondRandom).isSameAs(randomSource.getRandom(secondSeed));
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then(firstRandom).isNotSameAs(secondRandom);
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}
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@Property
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void manySeedsDoNotCauseMemoryLeak(@ForAll @LongRange(min = 1L) long initialSeed) {
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// given
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RandomSource randomSource = new DeterministicRandomSource(initialSeed);
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// when
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for (int i = 0; i < 100; i++) {
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randomSource.nextSeed();
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}
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// then
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// If no OutOfMemoryError occurs, the cache is properly managed
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then(randomSource).isNotNull();
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}
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@Property
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void sameInitialSeedProducesSameSeedSequence(@ForAll @LongRange(min = 1L) long initialSeed) {
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// given
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RandomSource randomSource1 = new DeterministicRandomSource(initialSeed);
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RandomSource randomSource2 = new DeterministicRandomSource(initialSeed);
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// when
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long seed1 = randomSource1.nextSeed();
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long seed2 = randomSource2.nextSeed();
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// then
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then(seed1).isEqualTo(seed2);
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}
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@Property
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void cachedRandomInstanceProducesDeterministicValues(@ForAll @LongRange(min = 1L) long initialSeed) {
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// given
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RandomSource randomSource = new DeterministicRandomSource(initialSeed);
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long seed = randomSource.nextSeed();
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// when
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Random cached1 = randomSource.getRandom(seed);
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Random cached2 = randomSource.getRandom(seed);
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// then
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then(cached1).isSameAs(cached2);
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int value1 = cached1.nextInt();
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int value2 = cached2.nextInt();
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then(value1).isNotEqualTo(value2); // Same instance, so state progresses
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}
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@Property
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void multipleSeedsAreStoredIndependently(@ForAll @LongRange(min = 1L) long initialSeed) {
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// given
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RandomSource randomSource = new DeterministicRandomSource(initialSeed);
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// when
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long seed1 = randomSource.nextSeed();
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long seed2 = randomSource.nextSeed();
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long seed3 = randomSource.nextSeed();
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// then
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Random random1 = randomSource.getRandom(seed1);
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Random random2 = randomSource.getRandom(seed2);
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Random random3 = randomSource.getRandom(seed3);
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then(random1).isNotNull();
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then(random2).isNotNull();
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then(random3).isNotNull();
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then(random1).isNotSameAs(random2);
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then(random2).isNotSameAs(random3);
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}
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@Property
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void getRandomReturnsNullForUncachedSeed(@ForAll @LongRange(min = 1L) long initialSeed) {
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// given
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RandomSource randomSource = new DeterministicRandomSource(initialSeed);
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// when
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Random random = randomSource.getRandom(999999999L);
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// then
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then(random).isNull();
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}
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}

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