Resolve #38 - Fix issues, include file & add test coverage

This resolves the problem where a file was accidentally not included
in the compiled library.  It also had a few issues/bugs which were not
apparent previously (because it had not been built).

I have also added some happy-path test coverage for it as well, while
I was re-enabling it anyway.

Author: craigfowler

CSF.Entities/CSF.Entities.csproj

@@ -49,9 +49,6 @@
       <LogicalName>Strings.resx.resources</LogicalName>
     </EmbeddedResource>
   </ItemGroup>
-  <ItemGroup>
-    <Compile Remove="Identity.cs" />
-  </ItemGroup>
   <ItemGroup>
     <Compile Condition=" '$(EnableDefaultCompileItems)' == 'true' " Update="Resources\ExceptionMessages.Designer.cs">
       <DependentUpon>ExceptionMessages.resx</DependentUpon>
@@ -63,7 +60,4 @@
   <ItemGroup>
     <Folder Include="Resources\" />
   </ItemGroup>
-  <ItemGroup>
-    <None Include="Identity.cs" Condition=" '$(EnableDefaultCompileItems)' == 'true' " />
-  </ItemGroup>
 </Project>

CSF.Entities/Identity.cs

@@ -37,7 +37,7 @@ public static class Identity
     {
         static readonly IGetsIdentityType identityTypeProvider = new IdentityTypeProvider();
         static readonly ICreatesIdentity identityFactory = new IdentityFactory();
-        static readonly IUpCastsIdentity caster = new IdentityCaster();
+        static readonly ICastsIdentityType caster = new IdentityTypeCaster();
         static readonly IParsesIdentity parser = new IdentityParser();
 
         /// <summary>
@@ -69,7 +69,7 @@ public static IIdentity<TEntity> Parse<TEntity>(object value) where TEntity : IE
         /// <param name="identity">The identity to convert to a different entity type.</param>
         /// <typeparam name="TCast">The desired entity type.</typeparam>
         /// <exception cref="InvalidCastException">If the <paramref name="identity"/> is not suitable for the entity type <typeparamref name="TCast"/>.</exception>
-        public static IIdentity<TCast> Cast<TCast>(this IIdentity identity)
+        public static IIdentity<TCast> Cast<TCast>(this IIdentity identity) where TCast : IEntity
             => caster.CastIdentity<TCast>(identity);
     }
 }

Tests/CSF.Entities.Tests/IdentityTests.cs

@@ -37,6 +37,7 @@ public void Equals_returns_false_for_two_identities_with_incompatible_entity_typ
             var identity2 = new Identity<long, Person>(5);
             Assert.That(identity1.Equals(identity2), Is.False);
         }
+
         [Test, AutoMoqData]
         public void Equals_operator_returns_true_for_two_equal_identities()
         {
@@ -69,6 +70,27 @@ public void Equals_operator_returns_false_for_two_identities_with_incompatible_e
             Assert.That(identity1 == identity2, Is.False);
         }
 
+        [Test, AutoMoqData]
+        public void Create_creates_identity_with_correct_value()
+        {
+            var identity = Identity.Create<Cat>(5);
+            Assert.That(identity.Value, Is.EqualTo(5));
+        }
+
+        [Test, AutoMoqData]
+        public void Parse_returns_identity_with_correct_value()
+        {
+            var identity = Identity.Parse<Cat>("66");
+            Assert.That(identity.Value, Is.EqualTo(66));
+        }
+
+        [Test, AutoMoqData]
+        public void Cast_returns_appropriate_identity()
+        {
+            var identity = new Identity<long,Animal>(5);
+            Assert.That(() => Identity.Cast<Cat>(identity).Value, Is.EqualTo(5));
+        }
+
         [Test, AutoMoqData]
         public void GetValueAsString_returns_correct_value()
         {