yunit package cannot be referenced by a test shared lib

[928PJY]

If a test shared library references the yunit package, it will be treated as a test project like following.

And the following error will be thrown from the test discovery (not in project build report).

Microsoft.VisualStudio.TestPlatform.ObjectModel.TestPlatformException: Could not find testhost
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Hosting.DotnetTestHostManager.GetTestHostProcessStartInfo(IEnumerable`1 sources, IDictionary`2 environmentVariables, TestRunnerConnectionInfo connectionInfo) in /_/src/Microsoft.TestPlatform.TestHostProvider/Hosting/DotnetTestHostManager.cs:line 406
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.ProxyOperationManager.SetupChannel(IEnumerable`1 sources, String runSettings) in /_/src/Microsoft.TestPlatform.CrossPlatEngine/Client/ProxyOperationManager.cs:line 223
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.ProxyDiscoveryManager.InitializeDiscovery(DiscoveryCriteria discoveryCriteria, ITestDiscoveryEventsHandler2 eventHandler, Boolean skipDefaultAdapters) in /_/src/Microsoft.TestPlatform.CrossPlatEngine/Client/ProxyDiscoveryManager.cs:line 149