Why is it not working with opencover?

Author: paulpach

appveyor.yml

@@ -14,8 +14,7 @@ artifacts:
 image: Visual Studio 2017
 
 test_script:
-  - nunit3-console.exe MLAPI.Tests\bin\Debug\MLAPI.Tests.dll
-# - .\packages\OpenCover.4.6.519\tools\OpenCover.Console.exe -register:user -target:"nunit3-console.exe" -targetargs:"MLAPI.Tests\bin\Debug\MLAPI.Tests.dll" -output:"coverage.xml" -filter:"+[MLAPI*]* -[MLAPI.Tests*]* -returntargetcode"
+  - .\packages\OpenCover.4.6.519\tools\OpenCover.Console.exe -returntargetcode -register:user -target:"nunit3-console.exe" -targetargs:"MLAPI.Tests\bin\Debug\MLAPI.Tests.dll" -output:"coverage.xml" -filter:"+[MLAPI*]* -[MLAPI.Tests*]* "
 
 
 after_test: