Make fully loosely coupled by Dependency Injection

Author: Tarak-Chandra-Sarkar

UnitTestingUsingNUnitWithMoq/CreditDecision.cs

@@ -4,10 +4,11 @@ namespace UnitTestingUsingNUnitWithMoq
 {
     public class CreditDecision
     {
-        readonly CreditDecisionService creditDecisionService;
+        readonly ICreditDecisionService creditDecisionService;
 
-        // We have made this loosely coupled but can not inject Moq instance instead of CreditDecisionService
-        public CreditDecision(CreditDecisionService creditDecisionService)
+        // This assumes that there is an existing ICreditDecisionService interface
+        // and that CreditDecisionService implements it.
+        public CreditDecision(ICreditDecisionService creditDecisionService)
         {
             this.creditDecisionService = creditDecisionService;
         }

UnitTestingUsingNUnitWithMoq/CreditDecisionService.cs

@@ -2,7 +2,7 @@
 
 namespace UnitTestingUsingNUnitWithMoq
 {
-    public class CreditDecisionService
+    public class CreditDecisionService : ICreditDecisionService
     {
         public CreditDecisionService()
         {

UnitTestingUsingNUnitWithMoq/ICreditDecisionService.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace UnitTestingUsingNUnitWithMoq
+{
+    public interface ICreditDecisionService
+    {
+        string GetCreditDecision(int creditScore);
+    }
+}

UnitTestingUsingNUnitWithMoq/UnitTestingUsingNUnitWithMoq.csproj

@@ -45,6 +45,7 @@
   <ItemGroup>
     <Compile Include="CreditDecision.cs" />
     <Compile Include="CreditDecisionService.cs" />
+    <Compile Include="ICreditDecisionService.cs" />
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>