test: add inspect-brk option to cluster module

Ensure that cluster interoperates with the --inspect-brk option.
This does not test for --debug-brk.

Fixes: https://github.com/nodejs/node/issues/11420
PR-URL: https://github.com/nodejs/node/pull/12503
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/sequential/test-cluster-inspect-brk.js

@@ -0,0 +1,36 @@
+'use strict';
+const common = require('../common');
+
+// A test to ensure that cluster properly interoperates with the
+// --inspect-brk option.
+
+const assert = require('assert');
+const cluster = require('cluster');
+const debuggerPort = common.PORT;
+
+if (cluster.isMaster) {
+  function test(execArgv) {
+
+    cluster.setupMaster({
+      execArgv: execArgv,
+      stdio: ['pipe', 'pipe', 'pipe', 'ipc', 'pipe']
+    });
+
+    const worker = cluster.fork();
+
+    // Debugger listening on port [port].
+    worker.process.stderr.once('data', common.mustCall(function() {
+      worker.process.kill('SIGTERM');
+    }));
+
+    worker.process.on('exit', common.mustCall(function(code, signal) {
+      assert.strictEqual(signal, 'SIGTERM');
+    }));
+  }
+
+  test(['--inspect-brk']);
+  test([`--inspect-brk=${debuggerPort}`]);
+} else {
+  // Cluster worker is at a breakpoint, should not reach here.
+  assert.fail('Test failed: cluster worker should be at a breakpoint.');
+}