AppVeyor build config is broken

[acarteas]

AppVeyor build gets to the following lines:

 Total time: 17.7062 Seconds
C:\Program Files\dotnet\sdk\3.1.401\Microsoft.TestPlatform.targets(32,5): error MSB4181: The "Microsoft.TestPlatform.Build.Tasks.VSTestTask" task returned false but did not log an error. [C:\projects\filecache\src\FileCache.UnitTests\FileCache.UnitTests.csproj]
An error occurred when executing task 'Test'.
Error: One or more errors occurred.
	.NET Core CLI: Process returned an error (exit code 1).
Command exited with code 1

I'm guessing it's a config issue.

[acarteas]

Running the build manually on AppVeyor website appears to work. Leaving this one open as a wait and see.