diff --git a/Refactoring/Store.cs b/Refactoring/Store.cs
index d9a7c78..48fcad6 100644
--- a/Refactoring/Store.cs
+++ b/Refactoring/Store.cs
@@ -32,7 +32,7 @@ public void Purchase(string productId, int quantity)
                 throw new OutOfStockException();
             }
 
-            product.Quantity = product.Quantity - quantity+1;
+            product.Quantity = product.Quantity - quantity;
             user.Balance = user.Balance - product.Price * quantity;
 
             dataManager.SaveUser(user);
diff --git a/UnitTestProject/AuthenticatorTests.cs b/UnitTestProject/AuthenticatorTests.cs
new file mode 100644
index 0000000..bef19bf
--- /dev/null
+++ b/UnitTestProject/AuthenticatorTests.cs
@@ -0,0 +1,112 @@
+using Newtonsoft.Json;
+using NUnit.Framework;
+using Refactoring;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace UnitTestProject
+{
+    [TestFixture]
+    class AuthenticatorTests
+    {
+        private List<User> users;
+        private Authenticator authenticator;
+
+        [TestFixtureSetUp]
+        public void Initialize_Data()
+        {
+            users = new List<User>();
+            User testUser = new User();
+            testUser.Name = "Test User";
+            testUser.Password = "password";
+            testUser.Balance = 10.00;
+            users.Add(testUser);
+
+            authenticator = new Authenticator(users);
+        }
+
+        [Test]
+        public void Test_AuthenticateReturnsUserWithSuccessfulAuthenticate()
+        {
+            User returnUser;
+            //Act
+            returnUser = authenticator.Authenticate("Test User", "password");
+            //Assert
+            Assert.AreEqual(users[0], returnUser);
+        }
+
+        [Test]
+        public void Test_AuthenticateReturnsNullWithIncorrectName()
+        {
+            User returnUser;
+            //Act
+            returnUser = authenticator.Authenticate("User Test", "password");
+            //Assert
+            Assert.Null(returnUser);
+        }
+
+        [Test]
+        public void Test_AuthenticateReturnsNullWithWrongPassword()
+        {
+            User returnUser;
+            //Act
+            returnUser = authenticator.Authenticate("Test User", "");
+            //Assert
+            Assert.Null(returnUser);
+        }
+
+        [Test]
+        public void Test_AuthenticateReturnsNullWithNullName()
+        {
+            User returnUser;
+            //Act
+            returnUser = authenticator.Authenticate(null, "password");
+            //Assert
+            Assert.Null(returnUser);
+        }
+
+        [Test]
+        public void Test_AuthenticateReturnsUserWithNullPassword()
+        {
+            User returnUser;
+            //Act
+            returnUser = authenticator.Authenticate("Test User", null);
+            //Assert
+            Assert.AreEqual(users[0], returnUser);
+        }
+
+
+        // THE BELOW CODE IS REQUIRED TO PREVENT THE TESTS FROM MODIFYING THE USERS/PRODUCTS ON FILE
+        //  This is not a good unit testing pattern - the unit test dependency on the file system should
+        //  actually be broken ... training on how to do this will be coming.
+        private List<User> originalUsers;
+        private List<Product> originalProducts;
+
+        [SetUp]
+        public void Test_Initialize()
+        {
+            // Load users from data file
+            originalUsers = JsonConvert.DeserializeObject<List<User>>(File.ReadAllText(@"Data/Users.json"));
+
+            // Load products from data file
+            originalProducts = JsonConvert.DeserializeObject<List<Product>>(File.ReadAllText(@"Data/Products.json"));
+        }
+
+
+        [TearDown]
+        public void Test_Cleanup()
+        {
+            // Restore users
+            string json = JsonConvert.SerializeObject(originalUsers, Formatting.Indented);
+            File.WriteAllText(@"Data/Users.json", json);
+
+            // Restore products
+            string json2 = JsonConvert.SerializeObject(originalProducts, Formatting.Indented);
+            File.WriteAllText(@"Data/Products.json", json2);
+        }
+    }
+}
diff --git a/UnitTestProject/StoreTests.cs b/UnitTestProject/StoreTests.cs
index 9f0b866..9b6df5c 100644
--- a/UnitTestProject/StoreTests.cs
+++ b/UnitTestProject/StoreTests.cs
@@ -34,20 +34,34 @@ private Product createTestProduct(string id, string name, double price, int quan
             return testProduct;
         }
 
+        private const string TEST_PRODUCT_ID = "1";
+        private List<User> users;
+        private List<Product> products;
+        private DataManager dataManager;
+        private Store store;
+
+        [SetUp]
+        public void Initialize_Data()
+        {
+            users = new List<User>();
+            products = new List<Product>();
+        }
+
+        private void CreateStore()
+        {
+            dataManager = new DataManager(users, products);
+            store = new Store(users[0], dataManager);
+        }
+
         [Test]
         public void Test_PurchaseThrowsNoErrorForValidFunds()
         {
             //Arrange
-            const string TEST_PRODUCT_ID = "1";
-
-            var users = new List<User>();
             users.Add(createTestUser("Test User", "", 99.99));
 
-            var products = new List<Product>();
             products.Add(createTestProduct(TEST_PRODUCT_ID, "Product", 9.99, 10));
 
-            var dataManager = new DataManager(users, products);
-            var store = new Store(users[0], dataManager);
+            CreateStore();
 
             //Act
             store.Purchase(TEST_PRODUCT_ID, 10);
@@ -60,34 +74,74 @@ public void Test_PurchaseThrowsNoErrorForValidFunds()
         public void Test_PurchaseRemovesProductFromStore()
         {
             //Arrange
+            users.Add(createTestUser("Test User", "", 99.99));
+
+            products.Add(createTestProduct(TEST_PRODUCT_ID, "Product", 9.99, 10));
+
+            CreateStore();
 
             //Act
+            store.Purchase(TEST_PRODUCT_ID, 9);
 
             //Assert 
-            //(choose the appropriate statement(s))
-            //Assert.AreEqual(1, products[0].Quantity);
-            //Assert.AreSame(1, products[0].Quantity);
-            //Assert.IsTrue(products[0].Quantity == 1);
+            Assert.AreEqual(1, products[0].Quantity);
         }
 
         [Test]
         public void Test_PurchaseThrowsExceptionWhenBalanceIsTooLow()
         {
             //Arrange
+            users.Add(createTestUser("Test User", "", 1.00));
 
-            //Act
+            products.Add(createTestProduct(TEST_PRODUCT_ID, "Product", 1.01, 10));
 
-            //Assert
+            CreateStore();
+
+            InsufficientFundsException expectedException = new InsufficientFundsException();
+
+            //Act
+            try
+            {
+                store.Purchase(TEST_PRODUCT_ID, 1);
+                Assert.Fail();
+            }
+            catch(Exception e)
+            {
+                Assert.AreEqual(expectedException.Message, e.Message);
+            }
+           
         }
 
         [Test]
+        [ExpectedException(typeof(InsufficientFundsException))]
         public void Test_PurchaseThrowsExceptionWhenBalanceIsTooLowVersion2()
         {
             //Arrange
+            users.Add(createTestUser("Test User", "", 1.00));
+
+            products.Add(createTestProduct(TEST_PRODUCT_ID, "Product", 1.01, 10));
+
+            CreateStore();
 
             //Act
+            store.Purchase(TEST_PRODUCT_ID, 1);
+
+        }
+
+        [Test]
+        [ExpectedException(typeof(OutOfStockException))]
+        public void Test_PurchaseThrowsExceptionWhenOutOfStock()
+        {
+            //Arrange
+            users.Add(createTestUser("Test User", "", 10.00));
+
+            products.Add(createTestProduct(TEST_PRODUCT_ID, "Product", 1.00, 0));
+
+            CreateStore();
+
+            //Act
+            store.Purchase(TEST_PRODUCT_ID, 1);
 
-            //Assert
         }
 
 
diff --git a/UnitTestProject/UnitTestProject.csproj b/UnitTestProject/UnitTestProject.csproj
index bcf3847..c695f54 100644
--- a/UnitTestProject/UnitTestProject.csproj
+++ b/UnitTestProject/UnitTestProject.csproj
@@ -35,6 +35,7 @@
     <WarningLevel>4</WarningLevel>
   </PropertyGroup>
   <ItemGroup>
+    <Reference Include="Microsoft.VisualStudio.QualityTools.UnitTestFramework, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL" />
     <Reference Include="Newtonsoft.Json, Version=8.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed, processorArchitecture=MSIL">
       <HintPath>..\packages\Newtonsoft.Json.8.0.2\lib\net45\Newtonsoft.Json.dll</HintPath>
       <Private>True</Private>
@@ -73,6 +74,7 @@
     <Compile Include="StoreTests.cs" />
     <Compile Include="IntegrationTests.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="AuthenticatorTests.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Refactoring\Tusc.csproj">