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 <cjihrig@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Trott · Feb 7, 2020 · Feb 4, 2020 · Feb 7, 2020 · 1d369a2031700d0b4ac94a6233ab51846ca59b80
commit 1d369a2031700d0b4ac94a6233ab51846ca59b80
diff --git a/test/parallel/test-dns-promises-lookupService.js b/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)$/ }
+);