Add test case to demonstrate memory-leak

package.json

@@ -4,9 +4,10 @@
   "description": "Bare bones Promises/A+ implementation",
   "main": "index.js",
   "scripts": {
-    "test": "mocha --timeout 200 --slow 99999",
+    "test": "mocha --timeout 200 --slow 99999 && npm run test-memory-leak",
     "test-resolve": "mocha test/resolver-tests.js -R spec --timeout 200 --slow 999999",
-    "test-extensions": "mocha test/extensions-tests.js -R spec --timeout 200 --slow 999999"
+    "test-extensions": "mocha test/extensions-tests.js -R spec --timeout 200 --slow 999999",
+    "test-memory-leak": "node --expose-gc test/memory-leak.js"
   },
   "repository": {
     "type": "git",

test/memory-leak.js

@@ -0,0 +1,41 @@
+'use strict';
+
+var assert = require('assert')
+var Promise = require('../')
+
+var i = 0
+var sampleA, sampleB
+
+function next() {
+  return new Promise(function (resolve) {
+    i++
+    /*
+    if (i % 100000 === 0) {
+      global.gc()
+      console.dir(process.memoryUsage())
+    }
+    */
+    if (i === 100000 && typeof global.gc === 'function') {
+      global.gc()
+      sampleA = process.memoryUsage()
+    }
+    if (i > 100000 * 5) {
+      if (typeof global.gc === 'function') {
+        global.gc()
+        sampleB = process.memoryUsage()
+        console.dir(sampleA)
+        console.dir(sampleB)
+        assert(sampleA.rss * 1.2 > sampleB.rss, 'RSS should not grow by more than 20%')
+        assert(sampleA.heapTotal * 1.2 > sampleB.heapTotal, 'heapTotal should not grow by more than 20%')
+        assert(sampleA.heapUsed * 1.2 > sampleB.heapUsed, 'heapUsed should not grow by more than 20%')
+      }
+    } else {
+      setImmediate(resolve)
+    }
+  }).then(next)
+}
+
+if (typeof global.gc !== 'function') {
+  console.warn('You must run with --expose-gc to test for memory leak.')
+}
+next().done()