diff --git a/affinity/src/test/java/net/openhft/affinity/impl/UtilitiesTest.java b/affinity/src/test/java/net/openhft/affinity/impl/UtilitiesTest.java
new file mode 100644
index 000000000..45d05dbfd
--- /dev/null
+++ b/affinity/src/test/java/net/openhft/affinity/impl/UtilitiesTest.java
@@ -0,0 +1,64 @@
+/*
+ * Copyright 2016-2025 chronicle.software
+ *
+ *  Licensed 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 net.openhft.affinity.impl;
+
+import org.junit.Test;
+
+import java.util.BitSet;
+
+import static org.junit.Assert.assertEquals;
+
+public class UtilitiesTest {
+
+    private static String hex(BitSet set, int... bits) {
+        set.clear();
+        for (int b : bits) {
+            set.set(b);
+        }
+        return Utilities.toHexString(set);
+    }
+
+    private static String bin(BitSet set, int... bits) {
+        set.clear();
+        for (int b : bits) {
+            set.set(b);
+        }
+        return Utilities.toBinaryString(set);
+    }
+
+    @Test
+    public void testToHexString() {
+        BitSet set = new BitSet();
+        assertEquals("", hex(set));
+        assertEquals("1", hex(set, 0));
+        assertEquals("10", hex(set, 4));
+        assertEquals(Long.toHexString(1L << 63), hex(set, 63));
+        assertEquals("01", hex(set, 64));
+        assertEquals("101", hex(set, 0, 128));
+    }
+
+    @Test
+    public void testToBinaryString() {
+        BitSet set = new BitSet();
+        assertEquals("", bin(set));
+        assertEquals("1", bin(set, 0));
+        assertEquals("10000", bin(set, 4));
+        assertEquals(Long.toBinaryString(1L << 63), bin(set, 63));
+        assertEquals("01", bin(set, 64));
+        assertEquals("101", bin(set, 0, 128));
+    }
+}