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Add cache with FIFO replacement policy (#6337)
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KevinMwita7
@@ -0,0 +1,330 @@
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package com.thealgorithms.datastructures.caches;
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import java.util.ArrayList;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Set;
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import java.util.concurrent.atomic.AtomicInteger;
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import org.junit.jupiter.api.Assertions;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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import org.junit.jupiter.api.function.Executable;
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class FIFOCacheTest {
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private FIFOCache<String, String> cache;
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private Set<String> evictedKeys;
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private List<String> evictedValues;
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@BeforeEach
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void setUp() {
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evictedKeys = new HashSet<>();
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evictedValues = new ArrayList<>();
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cache = new FIFOCache.Builder<String, String>(3)
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.defaultTTL(1000)
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.evictionListener((k, v) -> {
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evictedKeys.add(k);
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evictedValues.add(v);
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})
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.build();
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}
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@Test
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void testPutAndGet() {
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cache.put("a", "apple");
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Assertions.assertEquals("apple", cache.get("a"));
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}
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@Test
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void testOverwriteValue() {
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cache.put("a", "apple");
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cache.put("a", "avocado");
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Assertions.assertEquals("avocado", cache.get("a"));
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}
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@Test
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void testExpiration() throws InterruptedException {
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cache.put("temp", "value", 100);
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Thread.sleep(200);
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Assertions.assertNull(cache.get("temp"));
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Assertions.assertTrue(evictedKeys.contains("temp"));
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}
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@Test
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void testEvictionOnCapacity() {
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cache.put("a", "alpha");
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cache.put("b", "bravo");
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cache.put("c", "charlie");
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cache.put("d", "delta");
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int size = cache.size();
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Assertions.assertEquals(3, size);
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Assertions.assertEquals(1, evictedKeys.size());
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Assertions.assertEquals(1, evictedValues.size());
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}
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@Test
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void testEvictionListener() {
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cache.put("x", "one");
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cache.put("y", "two");
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cache.put("z", "three");
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cache.put("w", "four");
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Assertions.assertFalse(evictedKeys.isEmpty());
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Assertions.assertFalse(evictedValues.isEmpty());
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}
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@Test
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void testHitsAndMisses() {
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cache.put("a", "apple");
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Assertions.assertEquals("apple", cache.get("a"));
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Assertions.assertNull(cache.get("b"));
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Assertions.assertEquals(1, cache.getHits());
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Assertions.assertEquals(1, cache.getMisses());
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}
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@Test
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void testSizeExcludesExpired() throws InterruptedException {
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cache.put("a", "a", 100);
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cache.put("b", "b", 100);
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cache.put("c", "c", 100);
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Thread.sleep(150);
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Assertions.assertEquals(0, cache.size());
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}
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@Test
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void testSizeIncludesFresh() {
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cache.put("a", "a", 1000);
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cache.put("b", "b", 1000);
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cache.put("c", "c", 1000);
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Assertions.assertEquals(3, cache.size());
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}
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@Test
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void testToStringDoesNotExposeExpired() throws InterruptedException {
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cache.put("live", "alive");
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cache.put("dead", "gone", 100);
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Thread.sleep(150);
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String result = cache.toString();
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Assertions.assertTrue(result.contains("live"));
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Assertions.assertFalse(result.contains("dead"));
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}
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@Test
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void testNullKeyGetThrows() {
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Assertions.assertThrows(IllegalArgumentException.class, () -> cache.get(null));
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}
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@Test
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void testPutNullKeyThrows() {
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Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put(null, "v"));
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}
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@Test
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void testPutNullValueThrows() {
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Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put("k", null));
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}
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@Test
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void testPutNegativeTTLThrows() {
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Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put("k", "v", -1));
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}
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@Test
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void testBuilderNegativeCapacityThrows() {
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Assertions.assertThrows(IllegalArgumentException.class, () -> new FIFOCache.Builder<>(0));
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}
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@Test
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void testBuilderNullEvictionListenerThrows() {
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FIFOCache.Builder<String, String> builder = new FIFOCache.Builder<>(1);
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Assertions.assertThrows(IllegalArgumentException.class, () -> builder.evictionListener(null));
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}
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@Test
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void testEvictionListenerExceptionDoesNotCrash() {
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FIFOCache<String, String> listenerCache = new FIFOCache.Builder<String, String>(1).evictionListener((k, v) -> { throw new RuntimeException("Exception"); }).build();
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listenerCache.put("a", "a");
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listenerCache.put("b", "b");
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Assertions.assertDoesNotThrow(() -> listenerCache.get("a"));
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}
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@Test
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void testTtlZeroThrowsIllegalArgumentException() {
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Executable exec = () -> new FIFOCache.Builder<String, String>(3).defaultTTL(-1).build();
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Assertions.assertThrows(IllegalArgumentException.class, exec);
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}
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@Test
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void testPeriodicEvictionStrategyEvictsAtInterval() throws InterruptedException {
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FIFOCache<String, String> periodicCache = new FIFOCache.Builder<String, String>(10).defaultTTL(50).evictionStrategy(new FIFOCache.PeriodicEvictionStrategy<>(3)).build();
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periodicCache.put("x", "1");
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Thread.sleep(100);
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int ev1 = periodicCache.getEvictionStrategy().onAccess(periodicCache);
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int ev2 = periodicCache.getEvictionStrategy().onAccess(periodicCache);
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int ev3 = periodicCache.getEvictionStrategy().onAccess(periodicCache);
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Assertions.assertEquals(0, ev1);
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Assertions.assertEquals(0, ev2);
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Assertions.assertEquals(1, ev3, "Eviction should happen on the 3rd access");
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Assertions.assertEquals(0, periodicCache.size());
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}
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@Test
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void testPeriodicEvictionStrategyThrowsExceptionIfIntervalLessThanOrEqual0() {
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Executable executable = () -> new FIFOCache.Builder<String, String>(10).defaultTTL(50).evictionStrategy(new FIFOCache.PeriodicEvictionStrategy<>(0)).build();
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Assertions.assertThrows(IllegalArgumentException.class, executable);
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}
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@Test
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void testImmediateEvictionStrategyStrategyEvictsOnEachCall() throws InterruptedException {
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FIFOCache<String, String> immediateEvictionStrategy = new FIFOCache.Builder<String, String>(10).defaultTTL(50).evictionStrategy(new FIFOCache.ImmediateEvictionStrategy<>()).build();
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immediateEvictionStrategy.put("x", "1");
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Thread.sleep(100);
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int evicted = immediateEvictionStrategy.getEvictionStrategy().onAccess(immediateEvictionStrategy);
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Assertions.assertEquals(1, evicted);
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}
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@Test
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void testBuilderThrowsExceptionIfEvictionStrategyNull() {
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Executable executable = () -> new FIFOCache.Builder<String, String>(10).defaultTTL(50).evictionStrategy(null).build();
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Assertions.assertThrows(IllegalArgumentException.class, executable);
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}
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@Test
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void testReturnsCorrectStrategyInstance() {
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FIFOCache.EvictionStrategy<String, String> strategy = new FIFOCache.ImmediateEvictionStrategy<>();
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FIFOCache<String, String> newCache = new FIFOCache.Builder<String, String>(10).defaultTTL(1000).evictionStrategy(strategy).build();
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Assertions.assertSame(strategy, newCache.getEvictionStrategy(), "Returned strategy should be the same instance");
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}
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@Test
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void testDefaultStrategyIsImmediateEvictionStrategy() {
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FIFOCache<String, String> newCache = new FIFOCache.Builder<String, String>(5).defaultTTL(1000).build();
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Assertions.assertTrue(newCache.getEvictionStrategy() instanceof FIFOCache.ImmediateEvictionStrategy<String, String>, "Default strategy should be ImmediateEvictionStrategyStrategy");
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}
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@Test
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void testGetEvictionStrategyIsNotNull() {
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FIFOCache<String, String> newCache = new FIFOCache.Builder<String, String>(5).build();
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Assertions.assertNotNull(newCache.getEvictionStrategy(), "Eviction strategy should never be null");
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}
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@Test
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void testRemoveKeyRemovesExistingKey() {
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cache.put("A", "Alpha");
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cache.put("B", "Beta");
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Assertions.assertEquals("Alpha", cache.get("A"));
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Assertions.assertEquals("Beta", cache.get("B"));
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String removed = cache.removeKey("A");
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Assertions.assertEquals("Alpha", removed);
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Assertions.assertNull(cache.get("A"));
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Assertions.assertEquals(1, cache.size());
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}
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@Test
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void testRemoveKeyReturnsNullIfKeyNotPresent() {
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cache.put("X", "X-ray");
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Assertions.assertNull(cache.removeKey("NonExistent"));
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Assertions.assertEquals(1, cache.size());
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}
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@Test
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void testRemoveKeyHandlesExpiredEntry() throws InterruptedException {
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FIFOCache<String, String> expiringCache = new FIFOCache.Builder<String, String>(2).defaultTTL(100).evictionStrategy(new FIFOCache.ImmediateEvictionStrategy<>()).build();
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expiringCache.put("T", "Temporary");
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Thread.sleep(200);
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String removed = expiringCache.removeKey("T");
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Assertions.assertEquals("Temporary", removed);
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Assertions.assertNull(expiringCache.get("T"));
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}
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@Test
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void testRemoveKeyThrowsIfKeyIsNull() {
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Assertions.assertThrows(IllegalArgumentException.class, () -> cache.removeKey(null));
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}
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@Test
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void testRemoveKeyTriggersEvictionListener() {
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AtomicInteger evictedCount = new AtomicInteger();
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FIFOCache<String, String> localCache = new FIFOCache.Builder<String, String>(2).evictionListener((key, value) -> evictedCount.incrementAndGet()).build();
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localCache.put("A", "Apple");
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localCache.put("B", "Banana");
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localCache.removeKey("A");
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Assertions.assertEquals(1, evictedCount.get(), "Eviction listener should have been called once");
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}
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@Test
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void testRemoveKeyDoestNotAffectOtherKeys() {
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cache.put("A", "Alpha");
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cache.put("B", "Beta");
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cache.put("C", "Gamma");
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cache.removeKey("B");
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Assertions.assertEquals("Alpha", cache.get("A"));
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Assertions.assertNull(cache.get("B"));
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Assertions.assertEquals("Gamma", cache.get("C"));
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}
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@Test
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void testEvictionListenerExceptionDoesNotPropagate() {
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FIFOCache<String, String> localCache = new FIFOCache.Builder<String, String>(1).evictionListener((key, value) -> { throw new RuntimeException(); }).build();
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localCache.put("A", "Apple");
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Assertions.assertDoesNotThrow(() -> localCache.put("B", "Beta"));
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}
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@Test
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void testGetKeysReturnsAllFreshKeys() {
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cache.put("A", "Alpha");
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cache.put("B", "Beta");
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cache.put("G", "Gamma");
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Set<String> expectedKeys = Set.of("A", "B", "G");
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Assertions.assertEquals(expectedKeys, cache.getAllKeys());
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}
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@Test
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void testGetKeysIgnoresExpiredKeys() throws InterruptedException {
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cache.put("A", "Alpha");
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cache.put("B", "Beta");
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cache.put("G", "Gamma", 100);
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Set<String> expectedKeys = Set.of("A", "B");
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Thread.sleep(200);
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Assertions.assertEquals(expectedKeys, cache.getAllKeys());
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}
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@Test
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void testClearRemovesAllEntries() {
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cache.put("A", "Alpha");
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cache.put("B", "Beta");
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cache.put("G", "Gamma");
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cache.clear();
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Assertions.assertEquals(0, cache.size());
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}
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}
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