Added check for when the unit tests failed.

.gitignore

@@ -209,4 +209,7 @@ project.lock.json
 artifacts/
 
 #BenchmarkDotNet
-**/BenchmarkDotNet.Artifacts/
+**/BenchmarkDotNet.Artifacts/
+
+#CodeCoverage
+**/CodeCoverage/*

tests/CodeCoverage/CodeCoverage.cmd

@@ -12,7 +12,9 @@ cd ..
 cd ..
 
 rem The -threshold options prevents this taking ages...
-tests\CodeCoverage\OpenCover.4.6.519\tools\OpenCover.Console.exe -target:"C:\Program Files\dotnet\dotnet.exe" -targetargs:"test tests\ImageSharp.Tests -c Release -f net451" -threshold:10 -register:user -filter:"+[ImageSharp*]*" -excludebyattribute:*.ExcludeFromCodeCoverage* -hideskipped:All -output:.\ImageSharp.Coverage.xml
+tests\CodeCoverage\OpenCover.4.6.519\tools\OpenCover.Console.exe -target:"C:\Program Files\dotnet\dotnet.exe" -targetargs:"test tests\ImageSharp.Tests -c Release -f net451" -threshold:10 -register:user -filter:"+[ImageSharp*]*" -excludebyattribute:*.ExcludeFromCodeCoverage* -hideskipped:All -returntargetcode -output:.\ImageSharp.Coverage.xml
+
+if %errorlevel% neq 0 exit /b %errorlevel%
 
 SET PATH=C:\\Python34;C:\\Python34\\Scripts;%PATH%
 pip install codecov