Add tests for Murmur3 hash

References #348

Author: acogoluegnes

src/main/java/com/rabbitmq/stream/impl/HashUtils.java

@@ -26,6 +26,8 @@ private HashUtils() {}
   // https://github.com/apache/commons-codec/blob/rel/commons-codec-1.15/src/main/java/org/apache/commons/codec/digest/MurmurHash3.java
   static class Murmur3 implements ToIntFunction<String> {
 
+    private static final int DEFAULT_SEED = 104729;
+
     private static final int C1_32 = 0xcc9e2d51;
     private static final int C2_32 = 0x1b873593;
     private static final int R1_32 = 15;
@@ -57,12 +59,21 @@ private static int fmix32(int hash) {
       return hash;
     }
 
+    private final int seed;
+
+    Murmur3() {
+      this(DEFAULT_SEED);
+    }
+
+    Murmur3(int seed) {
+      this.seed = seed;
+    }
+
     @Override
     public int applyAsInt(String value) {
       byte[] data = value.getBytes(StandardCharsets.UTF_8);
       final int offset = 0;
       final int length = data.length;
-      final int seed = 104729;
       int hash = seed;
       final int nblocks = length >> 2;
 

src/test/java/com/rabbitmq/stream/impl/HashUtilsTest.java

@@ -0,0 +1,37 @@
+// Copyright (c) 2023 VMware, Inc. or its affiliates.  All rights reserved.
+//
+// This software, the RabbitMQ Stream Java client library, is dual-licensed under the
+// Mozilla Public License 2.0 ("MPL"), and the Apache License version 2 ("ASL").
+// For the MPL, please see LICENSE-MPL-RabbitMQ. For the ASL,
+// please see LICENSE-APACHE2.
+//
+// This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND,
+// either express or implied. See the LICENSE file for specific language governing
+// rights and limitations of this software.
+//
+// If you have any questions regarding licensing, please contact us at
+// [email protected].
+package com.rabbitmq.stream.impl;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+public class HashUtilsTest {
+
+  @ParameterizedTest
+  @CsvSource({"hello,1321743225", "brave,3825276426", "new,2970740106", "world,2453398188"})
+  void murmur3WithDefaultSeed(String input, String unsignedHash) {
+    int expectedHash = Integer.parseUnsignedInt(unsignedHash);
+    assertThat(HashUtils.MURMUR3.applyAsInt(input)).isEqualTo(expectedHash);
+  }
+
+  @ParameterizedTest
+  @CsvSource({"hello,3806057185", "brave,619588758", "new,1483300585", "world,1145629360"})
+  void murmur3WithSeed(String input, String unsignedHash) {
+    int expectedHash = Integer.parseUnsignedInt(unsignedHash);
+    HashUtils.Murmur3 hash = new HashUtils.Murmur3(42);
+    assertThat(hash.applyAsInt(input)).isEqualTo(expectedHash);
+  }
+}