test: send a bad record only after connection done

Connection is known to be completely setup only after data has
exchanged, so wait unil data echo before sending a bad record.
Otherwise, the bad record could interrupt completion of the server's
handshake, and whether the error is emitted on the connection or server
is a matter of timing.

Also, assert that server errors do not occur. 'error' would crash node
with and unhandled event, but 'tlsClientError' is ignored by default.

PR-URL: #25508
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-tls-alert-handling.js

@@ -43,6 +43,9 @@ server.listen(0, common.mustCall(function() {
   sendClient();
 }));
 
+server.on('tlsClientError', common.mustNotCall());
+
+server.on('error', common.mustNotCall());
 
 function sendClient() {
   const client = tls.connect(server.address().port, {
@@ -73,8 +76,10 @@ function sendBADTLSRecord() {
     socket: socket,
     rejectUnauthorized: false
   }, common.mustCall(function() {
-    socket.write(BAD_RECORD);
-    socket.end();
+    client.write('x');
+    client.on('data', (data) => {
+      socket.end(BAD_RECORD);
+    });
   }));
   client.on('error', common.mustCall());
 }