use "userland" punycode, plus tests

thanks to CenTdemeern1 for the `import` incantation

packages/backend/test/unit/UtilityService.ts

@@ -0,0 +1,39 @@
+import * as assert from 'assert';
+import { Test } from '@nestjs/testing';
+
+import { CoreModule } from '@/core/CoreModule.js';
+import { UtilityService } from '@/core/UtilityService.js';
+import { GlobalModule } from '@/GlobalModule.js';
+
+describe('UtilityService', () => {
+	let utilityService: UtilityService;
+
+	beforeAll(async () => {
+		const app = await Test.createTestingModule({
+			imports: [GlobalModule, CoreModule],
+		}).compile();
+		utilityService = app.get<UtilityService>(UtilityService);
+	});
+
+	describe('punyHost', () => {
+		test('simple', () => {
+			assert.equal(utilityService.punyHost('http://www.foo.com'),'www.foo.com');
+		});
+		test('japanese', () => {
+			assert.equal(utilityService.punyHost('http://www.新聞.com'),'www.xn--efvv70d.com');
+		});
+	});
+
+	describe('punyHostPSLDomain', () => {
+		test('simple', () => {
+			assert.equal(utilityService.punyHostPSLDomain('http://www.foo.com'),'foo.com');
+		});
+		test('japanese', () => {
+			assert.equal(utilityService.punyHostPSLDomain('http://www.新聞.com'),'xn--efvv70d.com');
+		});
+		test('lower', () => {
+			assert.equal(utilityService.punyHostPSLDomain('http://foo.github.io'),'foo.github.io');
+			assert.equal(utilityService.punyHostPSLDomain('http://foo.bar.github.io'),'bar.github.io');
+		});
+	});
+});