diff --git a/tests/utils/hex.test.mjs b/tests/utils/hex.test.mjs
new file mode 100644
index 00000000..0d6fe98f
--- /dev/null
+++ b/tests/utils/hex.test.mjs
@@ -0,0 +1,63 @@
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import {
+  normalizeHexString,
+  normalizeHexId,
+  normalizeHexPubkey,
+  HEX64_REGEX,
+} from "../../js/utils/hex.js";
+
+describe("hex utils", () => {
+  describe("normalizeHexString", () => {
+    it("should return empty string for non-string inputs", () => {
+      assert.equal(normalizeHexString(undefined), "");
+      assert.equal(normalizeHexString(null), "");
+      assert.equal(normalizeHexString(123), "");
+      assert.equal(normalizeHexString({}), "");
+    });
+
+    it("should return empty string for empty or whitespace-only strings", () => {
+      assert.equal(normalizeHexString(""), "");
+      assert.equal(normalizeHexString("   "), "");
+    });
+
+    it("should trim and lowercase valid hex strings", () => {
+      assert.equal(normalizeHexString("ABC"), "abc");
+      assert.equal(normalizeHexString("  DEF  "), "def");
+      assert.equal(normalizeHexString("AbCdEf"), "abcdef");
+    });
+  });
+
+  describe("aliases", () => {
+    it("should export normalizeHexId as an alias", () => {
+      assert.equal(normalizeHexId, normalizeHexString);
+    });
+
+    it("should export normalizeHexPubkey as an alias", () => {
+      assert.equal(normalizeHexPubkey, normalizeHexString);
+    });
+  });
+
+  describe("HEX64_REGEX", () => {
+    it("should match valid 64-character hex strings", () => {
+      const validHex = "a".repeat(64);
+      assert.match(validHex, HEX64_REGEX);
+      const mixedCase = "A".repeat(32) + "b".repeat(32);
+      assert.match(mixedCase, HEX64_REGEX);
+    });
+
+    it("should not match strings with incorrect length", () => {
+      assert.doesNotMatch("a".repeat(63), HEX64_REGEX);
+      assert.doesNotMatch("a".repeat(65), HEX64_REGEX);
+    });
+
+    it("should not match strings with non-hex characters", () => {
+      const invalidChar = "a".repeat(63) + "g";
+      assert.doesNotMatch(invalidChar, HEX64_REGEX);
+    });
+
+    it("should not match empty strings", () => {
+      assert.doesNotMatch("", HEX64_REGEX);
+    });
+  });
+});