OK - sometimes it just to confess - I took a chance, or didn’t know what I was doing - call it what you want.
In TFS Build-scripts there are a much nicer way of calling MSTest than the Exec-task as I suggested. There is already a task for it, called TestToolsTask. With this task you can much easier reach all the properties you need. And it even contains some undocumented features such as the TestContainer-property.
Here is my updated version on how to call the task:
<TestToolsTask
TestContainers="$(BinariesRoot)\Debug\Company.Service.Host.Test.Integration.dll"
BuildFlavor="%(ConfigurationToBuild.FlavorToBuild)"
Platform="%(ConfigurationToBuild.PlatformToBuild)"
PublishServer="$(TeamFoundationServerUrl)"
PublishBuild="$(BuildNumber)"
PathToResultsFilesRoot="$(TestResultsRoot)\..\IntegrationTestResults"
TeamProject="Betalningsplattformen2"
ContinueOnError="true"
/>