MSTest project won't compile with WinUI referenced

Describe the bug If you create an MSTest project and reference WinUI you get build errors making it impossible to use these APIs in testing.

Steps to reproduce the bug

1. Create a new MS Test .NET 5 test project
2. Add WinUI 3 Preview 4
3. Try and compile and observe these errors:

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(2451,5): warning MSB3842: Project "WinUITests" depends upon SDK "Visual C++ 2015-2019 UWP Desktop Runtime for native apps v14.0" which supports apps targeting "Windows 10.0". To verify whether "Visual C++ 2015-2019 UWP Desktop Runtime for native apps v14.0" is compatible with "Windows 10.0.18362.0", contact the SDK author or see http://go.microsoft.com/fwlink/?LinkID=309181.
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(2451,5): error MSB3843: Project "WinUITests" targets platform "Windows", but references SDK "Visual C++ 2015-2019 UWP Desktop Runtime for native apps v14.0" which targets platform "UAP".
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(2451,5): warning MSB3842: Project "WinUITests" depends upon SDK "Microsoft Universal CRT Debug Runtime v10.0.18362.0" which supports apps targeting "Windows 10.0". To verify whether "Microsoft Universal CRT Debug Runtime v10.0.18362.0" is compatible with "Windows 10.0.18362.0", contact the SDK author or see http://go.microsoft.com/fwlink/?LinkID=309181.
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(2451,5): error MSB3843: Project "WinUITests" targets platform "Windows", but references SDK "Microsoft Universal CRT Debug Runtime v10.0.18362.0" which targets platform "UAP".
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(2451,5): warning MSB3842: Project "WinUITests" depends upon SDK "Visual C++ 2015-2019 Runtime for Universal Windows Platform Apps v14.0" which supports apps targeting "Windows 10.0". To verify whether "Visual C++ 2015-2019 Runtime for Universal Windows Platform Apps v14.0" is compatible with "Windows 10.0.18362.0", contact the SDK author or see http://go.microsoft.com/fwlink/?LinkID=309181.
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(2451,5): error MSB3843: Project "WinUITests" targets platform "Windows", but references SDK "Visual C++ 2015-2019 Runtime for Universal Windows Platform Apps v14.0" which targets platform "UAP".

Full csproj:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net5.0-windows10.0.18362</TargetFramework>
    <TargetPlatformMinVersion>10.0.17134.0</TargetPlatformMinVersion>
    <IsPackable>false</IsPackable>
    <PlatformTarget>x64</PlatformTarget>
    <RootNamespace>WinUITests</RootNamespace>
    <RuntimeIdentifiers>win10-x86;win10-x64;win10-arm64</RuntimeIdentifiers>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.WinUI" Version="3.0.0-preview4.210210.4" />
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.1" />
    <PackageReference Include="MSTest.TestAdapter" Version="2.1.2" />
    <PackageReference Include="MSTest.TestFramework" Version="2.1.2" />
    <PackageReference Include="coverlet.collector" Version="3.0.3">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <Manifest Include="$(ApplicationManifest)" />
  </ItemGroup>

</Project>

Expected behavior Project compiles fine.

Screenshots

Version Info

NuGet package version: [Microsoft.WinUI 3.0.0-preview4.210210.4]

Windows app type:

UWP	Win32
	Yes

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
October 2020 Update (19042)	Yes
May 2020 Update (19041)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

Additional context

An alternative approach to reproduce is to create a new WinUI project and add this package to the project:

<PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.1" />

[dotMorten]

Thanks Scott. That makes way more sense

[Scottj1s]

Sorry - clarified wording