test: use mustCall() for simple flow tracking

Many of the tests use variables to track when callback functions
are invoked or events are emitted. These variables are then
asserted on process exit. This commit replaces this pattern in
straightforward cases with common.mustCall(). This makes the
tests easier to reason about, leads to a net reduction in lines
of code, and uncovered a few bugs in tests. This commit also
replaces some callbacks that should never be called with
common.fail().

PR-URL: https://github.com/nodejs/node/pull/7753
Reviewed-By: Wyatt Preul <wpreul@gmail.com>
Reviewed-By: Minwoo Jung <jmwsoft@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

1 files changed, 4 insertions, 29 deletions

diff --git a/test/parallel/test-cluster-worker-destroy.js b/test/parallel/test-cluster-worker-destroy.js
index 8e5ca63e13..c802177530 100644
--- a/test/parallel/test-cluster-worker-destroy.js
+++ b/test/parallel/test-cluster-worker-destroy.js
@@ -7,26 +7,18 @@
  * both code paths.
  */
 
-require('../common');
+const common = require('../common');
 var cluster = require('cluster');
-var assert = require('assert');
-
-var worker1, worker2, workerExited, workerDisconnected;
+var worker1, worker2;
 
 if (cluster.isMaster) {
   worker1 = cluster.fork();
   worker2 = cluster.fork();
 
-  workerExited = 0;
-  workerDisconnected = 0;
-
   [worker1, worker2].forEach(function(worker) {
-    worker.on('disconnect', ondisconnect);
-    worker.on('exit', onexit);
+    worker.on('disconnect', common.mustCall(function() {}));
+    worker.on('exit', common.mustCall(function() {}));
   });
-
-  process.on('exit', onProcessExit);
-
 } else {
   if (cluster.worker.id === 1) {
     // Call destroy when worker is disconnected
@@ -40,20 +32,3 @@ if (cluster.isMaster) {
     cluster.worker.destroy();
   }
 }
-
-function onProcessExit() {
-  assert.equal(workerExited,
-               2,
-               'When master exits, all workers should have exited too');
-  assert.equal(workerDisconnected,
-               2,
-               'When master exits, all workers should have disconnected');
-}
-
-function ondisconnect() {
-  ++workerDisconnected;
-}
-
-function onexit() {
-  ++workerExited;
-}