add tests

tests/MessagePack.Tests/MessagePack.Tests.csproj

@@ -135,6 +135,7 @@
     <Compile Include="SpecifiedFormatterResolverTest.cs" />
     <Compile Include="ToJsonTest.cs" />
     <Compile Include="UnionResolverTest.cs" />
+    <Compile Include="OldSpecBinaryFormatterTest.cs" />
     <Compile Include="UnsafeFormattersTest.cs" />
     <Compile Include="UnsafeMemoryTest.cs" />
     <Compile Include="Utils\ChainingAssertion.Ext.cs" />