diff --git a/test/utils.test.js b/test/utils.test.js
index 0d84bc480..33acd9844 100644
--- a/test/utils.test.js
+++ b/test/utils.test.js
@@ -1,5 +1,5 @@
 const assert = require("assert");
-const { getFromObjectCaseInsensitive } = require("../lib/build/utils");
+const { getFromObjectCaseInsensitive, getTopLevelDomainForSameSiteResolution } = require("../lib/build/utils");
 
 describe("SuperTokens utils test", () => {
     it("Test getFromObjectCaseInsensitive", () => {
@@ -18,3 +18,39 @@ describe("SuperTokens utils test", () => {
         assert.equal(getFromObjectCaseInsensitive("authoriZation", testObj), "test");
     });
 });
+
+describe("getTopLevelDomainForSameSiteResolution test", () => {
+    it('should return "localhost" for localhost URLs', () => {
+        assert.equal(getTopLevelDomainForSameSiteResolution("http://localhost:3000"), "localhost");
+        assert.equal(getTopLevelDomainForSameSiteResolution("https://localhost"), "localhost");
+    });
+
+    it('should return "localhost" for localhost.org URLs', () => {
+        assert.equal(getTopLevelDomainForSameSiteResolution("http://localhost.org"), "localhost");
+        assert.equal(getTopLevelDomainForSameSiteResolution("https://localhost.org/test-path"), "localhost");
+    });
+
+    it('should return "localhost" for IP addresses', () => {
+        assert.equal(getTopLevelDomainForSameSiteResolution("http://127.0.0.1"), "localhost");
+        assert.equal(getTopLevelDomainForSameSiteResolution("https://192.168.1.1"), "localhost");
+    });
+
+    it("should return the correct domain for normal URLs", () => {
+        assert.equal(getTopLevelDomainForSameSiteResolution("https://www.example.com"), "example.com");
+        assert.equal(getTopLevelDomainForSameSiteResolution("http://sub.domain.co.uk"), "domain.co.uk");
+    });
+
+    it("should handle .amazonaws.com domains correctly", () => {
+        assert.equal(getTopLevelDomainForSameSiteResolution("https://my-instance.amazonaws.com"), "amazonaws.com");
+    });
+
+    it("should handle .local domains correctly", () => {
+        assert.equal(getTopLevelDomainForSameSiteResolution("http://myserver.local"), "myserver.local");
+    });
+
+    it("should throw an error for invalid domains", () => {
+        assert.throws(() => {
+            getTopLevelDomainForSameSiteResolution("http://invalid..com");
+        }, Error);
+    });
+});