From efd1054a188d8b07cdee4097ee7c7fdc4b810ca2 Mon Sep 17 00:00:00 2001
From: Douglas Q Hawkins <douglas.hawkins@datadoghq.com>
Date: Mon, 29 Jun 2026 17:24:43 -0400
Subject: [PATCH] Add direct coverage tests for Hashtable.D2.Entry

Tests matches() with both true and false branches, and hash() for
consistency and key-sensitivity, since existing D2 operation tests
don't guarantee the false branch fires (different key pairs hash
to different buckets, so matches() is never called with a mismatch).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 .../datadog/trace/util/HashtableD2Test.java   | 33 +++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/internal-api/src/test/java/datadog/trace/util/HashtableD2Test.java b/internal-api/src/test/java/datadog/trace/util/HashtableD2Test.java
index 8605af1b33f..50da832395b 100644
--- a/internal-api/src/test/java/datadog/trace/util/HashtableD2Test.java
+++ b/internal-api/src/test/java/datadog/trace/util/HashtableD2Test.java
@@ -1,6 +1,7 @@
 package datadog.trace.util;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertSame;
@@ -118,6 +119,38 @@ void getOrCreateOnHitSkipsCreator() {
     assertEquals(0, createCount[0]);
   }
 
+  @Test
+  void entryMatchesTrueWhenBothKeysEqual() {
+    PairEntry entry = new PairEntry("a", 1, 100);
+    assertTrue(entry.matches("a", 1));
+  }
+
+  @Test
+  void entryMatchesFalseWhenKey1Differs() {
+    PairEntry entry = new PairEntry("a", 1, 100);
+    assertFalse(entry.matches("b", 1));
+  }
+
+  @Test
+  void entryMatchesFalseWhenKey2Differs() {
+    PairEntry entry = new PairEntry("a", 1, 100);
+    assertFalse(entry.matches("a", 2));
+  }
+
+  @Test
+  void entryHashIsConsistentForSameKeys() {
+    long h1 = Hashtable.D2.Entry.hash("x", 42);
+    long h2 = Hashtable.D2.Entry.hash("x", 42);
+    assertEquals(h1, h2);
+  }
+
+  @Test
+  void entryHashDiffersForDifferentKeys() {
+    long h1 = Hashtable.D2.Entry.hash("x", 1);
+    long h2 = Hashtable.D2.Entry.hash("x", 2);
+    assertFalse(h1 == h2);
+  }
+
   @Test
   void removeReturnsNullForMissingKey() {
     Hashtable.D2<String, Integer, PairEntry> table = new Hashtable.D2<>(8);