test: add unit tests for LimitedUniformReservoir

Co-Authored-By: Claude <noreply@anthropic.com>

Author: yanhom1314

test/test-core/src/test/java/org/dromara/dynamictp/test/core/metric/LimitedUniformReservoirTest.java

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.dromara.dynamictp.test.core.metric;
+
+import com.codahale.metrics.Snapshot;
+import org.dromara.dynamictp.core.metric.LimitedUniformReservoir;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * LimitedUniformReservoir test
+ *
+ * @author yanhom
+ * @since 1.2.2
+ */
+class LimitedUniformReservoirTest {
+
+    @Test
+    void testInitialState() {
+        LimitedUniformReservoir reservoir = new LimitedUniformReservoir();
+        assertEquals(0, reservoir.size());
+    }
+
+    @Test
+    void testUpdateIncrementsSize() {
+        LimitedUniformReservoir reservoir = new LimitedUniformReservoir();
+        reservoir.update(100);
+        assertEquals(1, reservoir.size());
+
+        reservoir.update(200);
+        assertEquals(2, reservoir.size());
+    }
+
+    @Test
+    void testSizeCappedAtDefaultSize() {
+        LimitedUniformReservoir reservoir = new LimitedUniformReservoir();
+        for (int i = 0; i < 5000; i++) {
+            reservoir.update(i);
+        }
+        // Should be capped at 4096
+        assertEquals(4096, reservoir.size());
+    }
+
+    @Test
+    void testGetSnapshot() {
+        LimitedUniformReservoir reservoir = new LimitedUniformReservoir();
+        reservoir.update(10);
+        reservoir.update(20);
+        reservoir.update(30);
+
+        Snapshot snapshot = reservoir.getSnapshot();
+        assertEquals(3, snapshot.size());
+        assertEquals(20.0, snapshot.getMedian(), 1.0);
+    }
+
+    @Test
+    void testGetSnapshotPercentiles() {
+        LimitedUniformReservoir reservoir = new LimitedUniformReservoir();
+        for (int i = 1; i <= 100; i++) {
+            reservoir.update(i);
+        }
+
+        Snapshot snapshot = reservoir.getSnapshot();
+        assertEquals(100, snapshot.size());
+        assertTrue(snapshot.getMedian() >= 40 && snapshot.getMedian() <= 60);
+        assertTrue(snapshot.get95thPercentile() >= 90);
+        assertTrue(snapshot.get99thPercentile() >= 95);
+    }
+
+    @Test
+    void testReset() {
+        LimitedUniformReservoir reservoir = new LimitedUniformReservoir();
+        reservoir.update(100);
+        reservoir.update(200);
+        assertEquals(2, reservoir.size());
+
+        reservoir.reset();
+        assertEquals(0, reservoir.size());
+    }
+
+    @Test
+    void testResetAndReuse() {
+        LimitedUniformReservoir reservoir = new LimitedUniformReservoir();
+        reservoir.update(100);
+        reservoir.reset();
+        reservoir.update(42);
+
+        Snapshot snapshot = reservoir.getSnapshot();
+        assertEquals(1, snapshot.size());
+        assertEquals(42, snapshot.getMedian(), 0.001);
+    }
+
+    @Test
+    void testConcurrentUpdates() throws InterruptedException {
+        LimitedUniformReservoir reservoir = new LimitedUniformReservoir();
+        int threadCount = 10;
+        int updatesPerThread = 500;
+        Thread[] threads = new Thread[threadCount];
+
+        for (int i = 0; i < threadCount; i++) {
+            threads[i] = new Thread(() -> {
+                for (int j = 0; j < updatesPerThread; j++) {
+                    reservoir.update(j);
+                }
+            });
+            threads[i].start();
+        }
+
+        for (Thread t : threads) {
+            t.join();
+        }
+
+        // All 5000 updates done, size should be capped at 4096
+        assertTrue(reservoir.size() <= 4096);
+        assertTrue(reservoir.size() > 0);
+    }
+}