test: add test-dns-promises-lookupService

This adds covereage for the onlookupservice() callback in
lib/internal/dns/promises.js. Because of stubbing in other tests, it is
not currently covered.

This test works on my local development machine with the network turned
off, so I'm putting it in parallel. If CI proves more challenging, it
can be moved to the internet directory instead.

PR-URL: #31640
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Richard Lau <[email protected]>

test/parallel/test-dns-promises-lookupService.js

@@ -0,0 +1,19 @@
+'use strict';
+
+const common = require('../common');
+
+const assert = require('assert');
+const dnsPromises = require('dns').promises;
+
+dnsPromises.lookupService('127.0.0.1', 22).then(common.mustCall((result) => {
+  assert.strictEqual(result.service, 'ssh');
+  assert.strictEqual(typeof result.hostname, 'string');
+  assert.notStrictEqual(result.hostname.length, 0);
+}));
+
+// Use an IP from the RFC 5737 test range to cause an error.
+// Refs: https://tools.ietf.org/html/rfc5737
+assert.rejects(
+  () => dnsPromises.lookupService('192.0.2.1', 22),
+  { code: /^(?:ENOTFOUND|EAI_AGAIN)$/ }
+);