I installed the SlowCheetah package via nuget and added transform files for my web.config based on Build config. However, on building, the web.config does not get transform
Did you set the "copy to output directory" property of your transform files to "Do not copy" ? Please check also your project file.
In your project file the following entries should be added (depending the version you installed , in this case 2.5.7):
true
$([System.IO.Path]::GetFullPath( $(MSBuildProjectDirectory)\..\packages\SlowCheetah.2.5.7\tools\SlowCheetah.Transforms.targets ))
$(SlowCheetah_NuGetImportPath)