Improve build batch file

appveyor.cmd

@@ -1,13 +1,14 @@
 @setlocal
 @pushd %~dp0
 
-nuget restore
+nuget restore || exit /b
 
-msbuild -p:Configuration=Release -t:Restore
+msbuild -p:Configuration=Release -t:Restore || exit /b
 
-msbuild -p:Configuration=Release src\test\WixToolsetTest.DirectX\WixToolsetTest.DirectX.csproj
+msbuild -p:Configuration=Release src\test\WixToolsetTest.DirectX\WixToolsetTest.DirectX.csproj || exit /b
+dotnet test -c Release --no-build src\test\WixToolsetTest.DirectX || exit /b
 
-msbuild -p:Configuration=Release -t:Pack src\wixext\WixToolset.DirectX.wixext.csproj
+msbuild -p:Configuration=Release -t:Pack src\wixext\WixToolset.DirectX.wixext.csproj || exit /b
 
 @popd
 @endlocal

nuget.config

@@ -2,6 +2,7 @@
 <configuration>
   <packageSources>
     <clear />
+    <add key="wixtoolset-burn" value="https://ci.appveyor.com/nuget/wixtoolset-burn" />
     <add key="wixtoolset-data" value="https://ci.appveyor.com/nuget/wixtoolset-data" />
     <add key="wixtoolset-extensibility" value="https://ci.appveyor.com/nuget/wixtoolset-extensibility" />
     <add key="wixtoolset-core" value="https://ci.appveyor.com/nuget/wixtoolset-core" />