Fixing GetCart for non-existing user

Now GetCart returns an empty cart for non-existing user
(user that haven't added anything to the cart before)
Added test to cover that

Also enhanced windows script for running cart service locally.
Now we have two options:
 - Running the service and redis locally (assuming redis emulator is installed)
   This is good for easier local debugging and troubleshooting

   docker_setup local

 - Running the service and redis in two separate docker containers
   This is good for better simulation of what will happen in the cloud

src/cartservice/cartstore/RedisCartStore.cs

@@ -69,13 +69,13 @@ namespace cartservice.cartstore
             // Access the cart from the cache
             var value = await db.HashGetAsync(userId, CART_FIELD_NAME);
 
-            Hipstershop.Cart cart = null;
             if (!value.IsNull)
             {
-                cart = Hipstershop.Cart.Parser.ParseFrom(value);
+                return Hipstershop.Cart.Parser.ParseFrom(value);
             }
 
-            return cart;
+            // We decided to return empty cart in cases when user wasn't in the cache before
+            return new Hipstershop.Cart();
         }
     }
 }

src/cartservice/scripts/docker_setup.bat

@@ -1,16 +1,45 @@
 @echo off
 
+set ENV=%1
+
+IF %ENV%==local GOTO local
+IF %ENV%==docker GOTO  docker_local
+GOTO End1
+
+:local
   set REDIS_PORT=6379
-set REDIS_ADDR=172.30.147.193
+  set REDIS_ADDR=localhost:%REDIS_PORT%
   set CART_SERVICE_ADDR=127.0.0.1
   set CART_SERVICE_PORT=7070
 
-rem run docker container with redis
-rem docker run -d --name=redis -p %REDIS_PORT%:%REDIS_PORT% redis:alpine
+  echo running redis emulator locally on a separate window
+  taskkill /f /im "redis-server.exe"
+  start redis-server
 
-rem running locally
+  echo running the cart service locally
   dotnet build ..\.
   dotnet run --project ../cartservice.csproj start
+GOTO End1
+
+:docker_local
+  set REDIS_PORT=6379
+  set REDIS_ADDR=redis:%REDIS_PORT%
+  set CART_SERVICE_ADDR=127.0.0.1
+  set CART_SERVICE_PORT=7070
+
+  echo run docker container with redis
+  docker run -d --name=redis -p %REDIS_PORT%:%REDIS_PORT% redis
+
+  echo building container image for cart service
+  docker build -t cartservice ..\.
+
+  echo run container image for cart service
+  docker run -it --rm -e REDIS_ADDR=%REDIS_ADDR% -e CART_SERVICE_ADDR=%CART_SERVICE_ADDR% -e CART_SERVICE_PORT=%CART_SERVICE_PORT% -p %CART_SERVICE_PORT%:%CART_SERVICE_PORT% cartservice
+
+GOTO End1
+
+:End1
+
 rem run docker container with cart service
 rem docker run -it --rm -e REDIS_ADDR=%REDIS_ADDR%:%REDIS_PORT% -e CART_SERVICE_ADDR=%CART_SERVICE_ADDR% -e CART_SERVICE_PORT=%CART_SERVICE_PORT% -p %CART_SERVICE_PORT%:%CART_SERVICE_PORT% cartservice
 rem -e GRPC_TRACE=all -e GRPC_VERBOSITY=debug

tests/cartservice/CartServiceTests.cs

@@ -12,6 +12,29 @@ namespace cartservice
         private static string serverHostName = "localhost";
         private static int port = 7070;
 
+        [Fact]
+        public async Task GetItem_NoAddItemBefore_EmptyCartReturned()
+        {
+            string userId = Guid.NewGuid().ToString();
+
+            // Construct server's Uri
+            string targetUri = $"{serverHostName}:{port}";
+
+            // Create a GRPC communication channel between the client and the server
+            var channel = new Channel(targetUri, ChannelCredentials.Insecure);
+
+            var client = new CartServiceClient(channel);
+
+            var request = new GetCartRequest
+            {
+                UserId = userId,
+            };
+            var cart = await client.GetCartAsync(request);
+            Assert.NotNull(cart);
+            // All grpc objects implement IEquitable, so we can compare equality with by-value semantics
+            Assert.Equal(new Cart(), cart);
+        }
+
         [Fact]
         public async Task AddItem_ItemInserted()
         {