Added IntAllocatorTests which exhibits stack overflow on original.

Author: Steve Powell

test/src/com/rabbitmq/utility/IntAllocatorTests.java

@@ -0,0 +1,92 @@
+//  The contents of this file are subject to the Mozilla Public License
+//  Version 1.1 (the "License"); you may not use this file except in
+//  compliance with the License. You may obtain a copy of the License
+//  at http://www.mozilla.org/MPL/
+//
+//  Software distributed under the License is distributed on an "AS IS"
+//  basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+//  the License for the specific language governing rights and
+//  limitations under the License.
+//
+//  The Original Code is RabbitMQ.
+//
+//  The Initial Developer of the Original Code is VMware, Inc.
+//  Copyright (c) 2011 VMware, Inc.  All rights reserved.
+//
+
+package com.rabbitmq.utility;
+
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Random;
+import java.util.Set;
+
+import junit.framework.TestCase;
+
+public class IntAllocatorTests extends TestCase {
+
+    private static final int TEST_ITERATIONS = 50000;
+    private static final int HI_RANGE = 100000;
+    private static final int LO_RANGE = 100;
+    private IntAllocator intAllocator = new IntAllocator(LO_RANGE, HI_RANGE);
+
+    private Random rand = new Random();
+
+    public void testReserveAndFree() throws Exception {
+        Set<Integer> set = new HashSet<Integer>();
+        for (int i = 0; i < TEST_ITERATIONS; ++i) {
+            int trial = getTrial();
+            if (set.contains(trial)) {
+                intAllocator.free(trial);
+                set.remove(trial);
+            } else {
+                assertTrue("Did not reserve free integer " + trial,
+                        intAllocator.reserve(trial));
+                set.add(trial);
+            }
+        }
+
+        for (int trial : set) {
+            assertFalse("Integer " + trial + " not allocated!",
+                    intAllocator.reserve(trial));
+        }
+    }
+
+    public void testAllocateAndFree() throws Exception {
+        Set<Integer> set = new HashSet<Integer>();
+        for (int i=0; i < TEST_ITERATIONS; ++i) {
+            if (getBool()) {
+                int trial = intAllocator.allocate();
+                assertFalse("Already allocated " + trial, set.contains(trial));
+                set.add(trial);
+            } else {
+                if (!set.isEmpty()) {
+                    int trial = extract(set);
+                    assertFalse("Allocator agreed to reserve " + trial,
+                            intAllocator.reserve(trial));
+                    intAllocator.free(trial);
+                }
+            }
+        }
+
+        for (int trial : set) {
+            assertFalse("Integer " + trial + " should be allocated!",
+                    intAllocator.reserve(trial));
+        }
+    }
+
+    private static int extract(Set<Integer> set) {
+        Iterator<Integer> iter = set.iterator();
+        int trial = iter.next();
+        iter.remove();
+        return trial;
+    }
+    
+    private int getTrial() {
+        return rand.nextInt(HI_RANGE-LO_RANGE+1) + LO_RANGE;
+    }
+    
+    private boolean getBool() {
+        return rand.nextBoolean();
+    }
+}