Xunit: Adding a project reference to my test project yields error CS0246: The type or namespace name 'Xunit' could not be found

[SurferJeffAtGoogle]

Code is here:
https://github.com/SurferJeffAtGoogle/csharp-docs-samples/tree/core/AuthSample/AuthTest

Running dotnet test in this directory works nicely:

> dotnet test
Build started, please wait...
Build completed.

Test run for C:\Users\rennie\gitrepos\dotnet-docs-samples\AuthSample\AuthTest\bin\Debug\netcoreapp2.0\AuthTest.d
ll(.NETCoreApp,Version=v2.0)
Microsoft (R) Test Execution Command Line Tool Version 15.3.0-preview-20170628-02
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
[xUnit.net 00:00:00.8725763]   Discovering: AuthTest
[xUnit.net 00:00:00.9823183]   Discovered:  AuthTest
[xUnit.net 00:00:01.0368701]   Starting:    AuthTest
[xUnit.net 00:00:01.2316710]   Finished:    AuthTest

Total tests: 1. Passed: 1. Failed: 0. Skipped: 0.
Test Run Successful.
Test execution time: 2.4182 Seconds

Until I try to add a project reference to the .csproj:

  <ItemGroup>
    <ProjectReference Include="..\AuthSample.csproj" />
  </ItemGroup>

Then, I get this error:

> dotnet test
Build started, please wait...
AuthTest\UnitTest1.cs(2,7): error CS0246: The type or namespace name 'Xunit' could not be found (are you missing
 a using directive or an assembly reference?) [C:\Users\rennie\gitrepos\dotnet-docs-samples\AuthSample\AuthSampl
e.csproj]
AuthTest\UnitTest1.cs(8,10): error CS0246: The type or namespace name 'FactAttribute' could not be found (are yo
u missing a using directive or an assembly reference?) [C:\Users\rennie\gitrepos\dotnet-docs-samples\AuthSample\
AuthSample.csproj]
AuthTest\UnitTest1.cs(8,10): error CS0246: The type or namespace name 'Fact' could not be found (are you missing
 a using directive or an assembly reference?) [C:\Users\rennie\gitrepos\dotnet-docs-samples\AuthSample\AuthSampl
e.csproj]

[bradwilson]

When I add the project reference, I get build failures:

The problem is that your projects are nested. If you make AuthSample and AuthTest peer folders, then everything works as expected.

[cppdev0000]

Stumbled here with this same problem, solution worked for me. Thanks.

[SurferJeffAtGoogle]

Thanks for the help!