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..e83bf6c
--- /dev/null
+++ b/UnitTestProject/AuthenticatorTests.cs
@@ -0,0 +1,79 @@
+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 Authenticator Authenticator;
+
+        [SetUp]
+        public void Test_Initialize()
+        {
+            List<User> users = new List<User>(5);
+            users.Add(new User() { Name = "User1", Password = "PW1", Balance = 0.00 });
+            users.Add(new User() { Name = "User2", Password = "PW2", Balance = 5.00 });
+            users.Add(new User() { Name = "User3", Password = "PW3", Balance = 10.00 });
+            users.Add(new User() { Name = "User4", Password = "PW4", Balance = 20.00 });
+            users.Add(new User() { Name = "User5", Password = "PW5", Balance = 30.00 });
+
+            Authenticator = new Authenticator(users);
+        }
+
+        [Test]
+        public void AuthenticateNullUser()
+        {
+            Assert.IsNull(Authenticator.Authenticate(null, ""));
+        }
+
+        [Test]
+        public void AuthenticateNullPassword()
+        {
+            Assert.IsNull(Authenticator.Authenticate("", null));
+        }
+
+        [Test]
+        public void AuthenticateBadPassword()
+        {
+            Assert.IsNull(Authenticator.Authenticate("User1", ""));
+        }
+
+        [Test]
+        public void AuthenticateUserDoesntExist()
+        {
+            Assert.IsNull(Authenticator.Authenticate("User6", "PW6"));
+        }
+
+        [Test]
+        public void AuthenticateFirstUser()
+        {
+            var user = Authenticator.Authenticate("User1", "PW1");
+            Assert.IsNotNull(user);
+            Assert.AreEqual("User1", user.Name);
+        }
+
+        [Test]
+        public void AuthenticateLastUser()
+        {
+            var user = Authenticator.Authenticate("User5", "PW5");
+            Assert.IsNotNull(user);
+            Assert.AreEqual("User5", user.Name);
+        }
+
+        [Test]
+        public void AuthenticateMiddleUser()
+        {
+            var user = Authenticator.Authenticate("User3", "PW3");
+            Assert.IsNotNull(user);
+            Assert.AreEqual("User3", user.Name);
+        }
+    }
+}
diff --git a/UnitTestProject/StoreTests.cs b/UnitTestProject/StoreTests.cs
index 9f0b866..66d91d6 100644
--- a/UnitTestProject/StoreTests.cs
+++ b/UnitTestProject/StoreTests.cs
@@ -34,21 +34,28 @@ private Product createTestProduct(string id, string name, double price, int quan
             return testProduct;
         }
 
-        [Test]
-        public void Test_PurchaseThrowsNoErrorForValidFunds()
+        private Store InitializeStore(string productId, double productPrice, int productQuantity, double userWallet )
         {
-            //Arrange
-            const string TEST_PRODUCT_ID = "1";
 
             var users = new List<User>();
-            users.Add(createTestUser("Test User", "", 99.99));
+            users.Add(createTestUser("Test User", "", userWallet));
 
             var products = new List<Product>();
-            products.Add(createTestProduct(TEST_PRODUCT_ID, "Product", 9.99, 10));
+            products.Add(createTestProduct(productId, "Product", productPrice, productQuantity));
 
             var dataManager = new DataManager(users, products);
             var store = new Store(users[0], dataManager);
 
+            return store;
+        }
+
+        [Test]
+        public void Test_PurchaseThrowsNoErrorForValidFunds()
+        {
+            //Arrange
+            const string TEST_PRODUCT_ID = "1";
+            var store = InitializeStore(TEST_PRODUCT_ID, 9.99, 10, 99.99);
+
             //Act
             store.Purchase(TEST_PRODUCT_ID, 10);
 
@@ -60,22 +67,30 @@ public void Test_PurchaseThrowsNoErrorForValidFunds()
         public void Test_PurchaseRemovesProductFromStore()
         {
             //Arrange
+            const string TEST_PRODUCT_ID = "1";
+            var store = InitializeStore(TEST_PRODUCT_ID, 9.99, 10, 99.99);
+            var product = store.GetProductById(TEST_PRODUCT_ID);
 
             //Act
+            store.Purchase(TEST_PRODUCT_ID, 9);
 
             //Assert 
             //(choose the appropriate statement(s))
-            //Assert.AreEqual(1, products[0].Quantity);
+            Assert.AreEqual(1, product.Quantity);
             //Assert.AreSame(1, products[0].Quantity);
             //Assert.IsTrue(products[0].Quantity == 1);
         }
 
         [Test]
+        [ExpectedException(typeof(InsufficientFundsException))]
         public void Test_PurchaseThrowsExceptionWhenBalanceIsTooLow()
         {
             //Arrange
+            const string TEST_PRODUCT_ID = "1";
+            var store = InitializeStore(TEST_PRODUCT_ID, 1.01, 1, 1.00);
 
             //Act
+            store.Purchase(TEST_PRODUCT_ID, 1);
 
             //Assert
         }
@@ -84,10 +99,38 @@ public void Test_PurchaseThrowsExceptionWhenBalanceIsTooLow()
         public void Test_PurchaseThrowsExceptionWhenBalanceIsTooLowVersion2()
         {
             //Arrange
+            const string TEST_PRODUCT_ID = "1";
+            var store = InitializeStore(TEST_PRODUCT_ID, 1.01, 1, 1.00);
 
             //Act
+            TestDelegate delegateThatThrows = new TestDelegate(() => store.Purchase(TEST_PRODUCT_ID, 1));
 
             //Assert
+            Assert.Throws<InsufficientFundsException>(delegateThatThrows);
+        }
+
+        [Test]
+        [ExpectedException(typeof(OutOfStockException))]
+        public void Test_PurchaseThrowsExceptionWhenOutOfStock()
+        {
+            //Arrange
+            const string TEST_PRODUCT_ID = "1";
+            var store = InitializeStore(TEST_PRODUCT_ID, 1.00, 0, 1.00);
+
+            //Act
+            store.Purchase(TEST_PRODUCT_ID, 1);
+        }
+
+        [Test]
+        [ExpectedException(typeof(OutOfStockException))]
+        public void Test_PurchaseThrowsExceptionWhenNotEnoughStock()
+        {
+            //Arrange
+            const string TEST_PRODUCT_ID = "1";
+            var store = InitializeStore(TEST_PRODUCT_ID, 1.00, 2, 3.00);
+
+            //Act
+            store.Purchase(TEST_PRODUCT_ID, 3);
         }
 
 
diff --git a/UnitTestProject/UnitTestProject.csproj b/UnitTestProject/UnitTestProject.csproj
index bcf3847..1a9e337 100644
--- a/UnitTestProject/UnitTestProject.csproj
+++ b/UnitTestProject/UnitTestProject.csproj
@@ -70,6 +70,7 @@
     <Otherwise />
   </Choose>
   <ItemGroup>
+    <Compile Include="AuthenticatorTests.cs" />
     <Compile Include="StoreTests.cs" />
     <Compile Include="IntegrationTests.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />