Index: test/domain.js
===================================================================
--- a/test/domain.js
+++ b/test/domain.js
@@ -18,28 +18,30 @@
 "use strict";
 
 // Only starting NodeJS 10 that URL is in the global space.
 const {URL} = require("url");
 const {createSandbox} = require("./_common");
 
 const publicSuffixes = require("../data/publicSuffixList.json");
 
+let normalizeHostname = null;
 let isThirdParty = null;
 let getDomain = null;
 
 exports.setUp = function(callback)
 {
   let sandboxedRequire = createSandbox({
     extraExports: {
       domain: ["getDomain"]
     }
   });
   (
-    {isThirdParty, getDomain} = sandboxedRequire("../lib/domain")
+    {normalizeHostname, isThirdParty,
+     getDomain} = sandboxedRequire("../lib/domain")
   );
 
   callback();
 };
 
 function hostnameToURL(hostname)
 {
   return new URL("http://" + hostname);
@@ -56,16 +58,40 @@
       // will fail if we don't normalize the document host as well.
       hostnameToURL(documentHostname).hostname
     ),
     expected,
     message
   );
 }
 
+exports.testNormalizeHostname = function(test)
+{
+  test.equal(normalizeHostname("example.com"), "example.com");
+  test.equal(normalizeHostname("example.com."), "example.com");
+  test.equal(normalizeHostname("example.com.."), "example.com");
+  test.equal(normalizeHostname("example.com..."), "example.com");
+
+  test.equal(normalizeHostname("Example.com"), "example.com");
+  test.equal(normalizeHostname("ExaMple.Com"), "example.com");
+  test.equal(normalizeHostname("ExaMple.Com.."), "example.com");
+
+  test.equal(normalizeHostname("192.168.1.1"), "192.168.1.1");
+  test.equal(normalizeHostname("192.168.1.1."), "192.168.1.1");
+
+  test.equal(normalizeHostname("2001:0db8:85a3:0000:0000:8a2e:0370:7334"),
+             "2001:0db8:85a3:0000:0000:8a2e:0370:7334");
+  test.equal(normalizeHostname("2001:0db8:85a3:0000:0000:8a2e:0370:7334."),
+             "2001:0db8:85a3:0000:0000:8a2e:0370:7334");
+  test.equal(normalizeHostname("2001:0DB8:85A3:0000:0000:8A2E:0370:7334"),
+             "2001:0db8:85a3:0000:0000:8a2e:0370:7334");
+
+  test.done();
+};
+
 exports.testIsThirdParty = function(test)
 {
   testThirdParty(test, "foo", "foo", false, "same domain isn't third-party");
   testThirdParty(test, "foo", "bar", true, "different domain is third-party");
   testThirdParty(test, "foo.com", "foo.com", false,
                  "same domain with TLD (.com) isn't third-party");
   testThirdParty(test, "foo.com", "bar.com", true,
                  "same TLD (.com) but different domain is third-party");