test: verify inspector help url works

This commit adds basic functionality testing of the
help URL printed when the inspector starts.

PR-URL: nodejs/node#19887
Refs: nodejs/node#19871
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Khaidi Chu <i@2333.moe>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/internet/test-inspector-help-page.js

@@ -0,0 +1,37 @@
+'use strict';
+const common = require('../common');
+
+common.skipIfInspectorDisabled();
+
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+const assert = require('assert');
+const https = require('https');
+const { spawnSync } = require('child_process');
+const child = spawnSync(process.execPath, ['--inspect', '-e', '""']);
+const stderr = child.stderr.toString();
+const helpUrl = stderr.match(/For help, see: (.+)/)[1];
+
+function check(url, cb) {
+  https.get(url, common.mustCall((res) => {
+    assert(res.statusCode >= 200 && res.statusCode < 400);
+
+    if (res.statusCode >= 300)
+      return check(res.headers.location, cb);
+
+    let result = '';
+
+    res.setEncoding('utf8');
+    res.on('data', (data) => {
+      result += data;
+    });
+
+    res.on('end', common.mustCall(() => {
+      assert(/>Debugging Guide</.test(result));
+      cb();
+    }));
+  })).on('error', common.mustNotCall);
+}
+
+check(helpUrl, common.mustCall());