diff --git a/stacks-queues/n-stacks.ipynb b/stacks-queues/n-stacks.ipynb
index 3c96414..1d57832 100644
--- a/stacks-queues/n-stacks.ipynb
+++ b/stacks-queues/n-stacks.ipynb
@@ -13,17 +13,20 @@
    "source": [
     "## Problem: Implement n stacks using a single array.\n",
     "\n",
-    "* [Clarifying Questions](#Clarifying-Questions)\n",
+    "* [Constraints and Assumptions](#Constraints-and-Assumptions)\n",
     "* [Test Cases](#Test-Cases)\n",
     "* [Algorithm](#Algorithm)\n",
-    "* [Code](#Code)"
+    "* [Code](#Code)\n",
+    "* [Unit Test](#Unit-Test)"
    ]
   },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Clarifying Questions\n",
+    "## Constraints and Assumptions\n",
+    "\n",
+    "*Problem statements are often intentionally ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
     "\n",
     "* Are the stacks and array a fixed size?\n",
     "    * Yes"
@@ -48,8 +51,13 @@
    "source": [
     "## Algorithm\n",
     "\n",
-    "* Initialize array\n",
-    "* Initialize stack pointers to -1\n",
+    "### Absolute Index\n",
+    "\n",
+    "* return stack size * stack index + stack pointer\n",
+    "\n",
+    "Complexity:\n",
+    "* Time: O(1)\n",
+    "* Space: O(1)\n",
     "\n",
     "### Push\n",
     "\n",
@@ -74,15 +82,6 @@
     "\n",
     "Complexity:\n",
     "* Time: O(1)\n",
-    "* Space: O(1)\n",
-    "\n",
-    "\n",
-    "### Absolute Index\n",
-    "\n",
-    "* return stack size * stack index + stack pointer\n",
-    "\n",
-    "Complexity:\n",
-    "* Time: O(1)\n",
     "* Space: O(1)"
    ]
   },
@@ -95,7 +94,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "metadata": {
     "collapsed": true
    },
@@ -130,39 +129,77 @@
     "            return data"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test\n",
+    "\n",
+    "*It is important to identify and run through general and edge cases from the [Test Cases](#Test-Cases) section by hand.  You generally will not be asked to write a unit test like what is shown below.*"
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {
     "collapsed": false
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Test: Pop on empty stack\n",
+      "Test: Push to full stack\n",
+      "Test: Push to non-full stack\n",
+      "Test: Pop on non-empty stack\n",
+      "Success: test_stacks\n",
+      "\n"
+     ]
+    }
+   ],
    "source": [
-    "num_stacks = 3\n",
-    "stack_size = 100\n",
-    "print('Pop on empty stack')\n",
-    "stacks = Stacks(num_stacks, stack_size)\n",
-    "try:\n",
-    "    stacks.pop(0)\n",
-    "except Exception as e:\n",
-    "    print(e)\n",
-    "print('Push to non-full stack')\n",
-    "stacks.push(0, 1)\n",
-    "stacks.push(0, 2)\n",
-    "stacks.push(1, 3)\n",
-    "stacks.push(2, 4)\n",
-    "print('Pop on non-empty stack')\n",
-    "print(stacks.pop(0))\n",
-    "print(stacks.pop(0))\n",
-    "print(stacks.pop(1))\n",
-    "print(stacks.pop(2))\n",
-    "print('Push to full stack')\n",
-    "for i in xrange(0, stack_size):\n",
-    "    stacks.push(2, i)\n",
-    "try:\n",
-    "    stacks.push(2, stack_size)\n",
-    "except Exception as e:\n",
-    "    print(e)"
+    "from nose.tools import assert_equal\n",
+    "from nose.tools import raises\n",
+    "\n",
+    "class Test(object):\n",
+    "    @raises(Exception)\n",
+    "    def test_pop_on_empty(self, num_stacks, stack_size):\n",
+    "        print('Test: Pop on empty stack')\n",
+    "        stacks = Stacks(num_stacks, stack_size)\n",
+    "        stacks.pop(0)\n",
+    "\n",
+    "    @raises(Exception)\n",
+    "    def test_push_on_full(self, num_stacks, stack_size):\n",
+    "        print('Test: Push to full stack')\n",
+    "        stacks = Stacks(num_stacks, stack_size)\n",
+    "        for i in xrange(0, stack_size):\n",
+    "            stacks.push(2, i)\n",
+    "        stacks.push(2, stack_size)\n",
+    "\n",
+    "    def test_stacks(self, num_stacks, stack_size):\n",
+    "        print('Test: Push to non-full stack')\n",
+    "        stacks = Stacks(num_stacks, stack_size)\n",
+    "        stacks.push(0, 1)\n",
+    "        stacks.push(0, 2)\n",
+    "        stacks.push(1, 3)\n",
+    "        stacks.push(2, 4)\n",
+    "\n",
+    "        print('Test: Pop on non-empty stack')\n",
+    "        assert_equal(stacks.pop(0), 2)\n",
+    "        assert_equal(stacks.pop(0), 1)\n",
+    "        assert_equal(stacks.pop(1), 3)\n",
+    "        assert_equal(stacks.pop(2), 4)\n",
+    "\n",
+    "        print('Success: test_stacks\\n')\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    num_stacks = 3\n",
+    "    stack_size = 100    \n",
+    "    test = Test()\n",
+    "    test.test_pop_on_empty(num_stacks, stack_size)\n",
+    "    test.test_push_on_full(num_stacks, stack_size)\n",
+    "    test.test_stacks(num_stacks, stack_size)"
    ]
   }
  ],