test: fix debug-port-cluster flakiness

Rewrite the test so that stderr reordering of the child processes won't
confuse the test's expectations.

PR-URL: #4310
Reviewed-By: Colin Ihrig <[email protected]>

test/parallel/test-debug-port-cluster.js

@@ -3,47 +3,25 @@ var common = require('../common');
 var assert = require('assert');
 var spawn = require('child_process').spawn;
 
-var port = common.PORT + 1337;
+const PORT_MIN = common.PORT + 1337;
+const PORT_MAX = PORT_MIN + 2;
 
 var args = [
-  '--debug=' + port,
+  '--debug=' + PORT_MIN,
   common.fixturesDir + '/clustered-server/app.js'
 ];
 
-var child = spawn(process.execPath, args);
-var outputLines = [];
+const child = spawn(process.execPath, args);
+child.stderr.setEncoding('utf8');
 
-child.stderr.on('data', function(data) {
-  var lines = data.toString().replace(/\r/g, '').trim().split('\n');
-  var line = lines[0];
-
-  lines.forEach(function(ln) { console.log('> ' + ln); } );
-
-  if (line === 'all workers are running') {
-    assertOutputLines();
-    process.exit();
-  } else {
-    outputLines = outputLines.concat(lines);
-  }
-});
-
-process.on('exit', function onExit() {
-  child.kill();
+let stderr = '';
+child.stderr.on('data', data => {
+  stderr += data;
+  if (child.killed !== true && stderr.includes('all workers are running'))
+    child.kill();
 });
 
-var assertOutputLines = common.mustCall(function() {
-  var expectedLines = [
-    'Debugger listening on port ' + port,
-    'Debugger listening on port ' + (port + 1),
-    'Debugger listening on port ' + (port + 2),
-  ];
-
-  // Do not assume any particular order of output messages,
-  // since workers can take different amout of time to
-  // start up
-  outputLines.sort();
-
-  assert.equal(outputLines.length, expectedLines.length);
-  for (var i = 0; i < expectedLines.length; i++)
-    assert.equal(outputLines[i], expectedLines[i]);
+process.on('exit', () => {
+  for (let port = PORT_MIN; port <= PORT_MAX; port += 1)
+    assert(stderr.includes(`Debugger listening on port ${port}`));
 });