test: fix test-net-socket-constructor

So it doesn't fail when creating a socket whose `fd` is already
being watched. Test that functionality now inside a cluster
worker.

Refs: libuv/libuv#1851
Refs: libuv/libuv#1897
PR-URL: #21466
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-net-socket-constructor.js

@@ -2,6 +2,7 @@
 
 const common = require('../common');
 const assert = require('assert');
+const cluster = require('cluster');
 const net = require('net');
 
 common.expectsError(() => {
@@ -25,27 +26,40 @@ function test(sock, readable, writable) {
   assert.strictEqual(socket.writable, writable);
 }
 
-test(undefined, false, false);
+if (cluster.isMaster) {
+  test(undefined, false, false);
 
-const server = net.createServer(common.mustCall((socket) => {
-  test(socket, true, true);
-  test({ handle: socket._handle }, false, false);
-  test({ handle: socket._handle, readable: true, writable: true }, true, true);
-  if (socket._handle.fd >= 0) {
-    test(socket._handle.fd, false, false);
-    test({ fd: socket._handle.fd }, false, false);
-    test({ fd: socket._handle.fd, readable: true, writable: true }, true, true);
-  }
+  const server = net.createServer(common.mustCall((socket) => {
+    socket.unref();
+    test(socket, true, true);
+    test({ handle: socket._handle }, false, false);
+    test({ handle: socket._handle, readable: true, writable: true },
+         true, true);
+    server.close();
+  }));
 
-  server.close();
-}));
+  server.listen(common.mustCall(() => {
+    const { port } = server.address();
+    const socket = net.connect(port, common.mustCall(() => {
+      test(socket, true, true);
+      socket.end();
+    }));
 
-server.listen(common.mustCall(() => {
-  const { port } = server.address();
-  const socket = net.connect(port, common.mustCall(() => {
-    test(socket, true, true);
-    socket.end();
+    test(socket, false, true);
   }));
 
-  test(socket, false, true);
-}));
+  cluster.setupMaster({
+    stdio: ['pipe', 'pipe', 'pipe', 'ipc', 'pipe', 'pipe', 'pipe']
+  });
+
+  const worker = cluster.fork();
+  worker.on('exit', common.mustCall((code, signal) => {
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
+  }));
+} else {
+  test(4, false, false);
+  test({ fd: 5 }, false, false);
+  test({ fd: 6, readable: true, writable: true }, true, true);
+  process.disconnect();
+}