Switch FSharp.Core.Unit tests to use Xunit (dotnet#9992)

Author: KevinRansom

tests/FSharp.Core.UnitTests/FSharp.Core.UnitTests.fsproj

@@ -21,7 +21,7 @@
     <LangVersion>preview</LangVersion>
 
     <DisableImplicitFSharpCoreReference>true</DisableImplicitFSharpCoreReference>
-    <UnitTestType>nunit</UnitTestType>
+    <UnitTestType>xunit</UnitTestType>
     <IsTestProject>true</IsTestProject>
     <IsPackable>true</IsPackable>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
@@ -38,7 +38,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <Compile Include="NUnitFrameworkShims.fs" />
+    <Compile Include="TestFrameworkHelpers.fs" />
     <Compile Include="LibraryTestFx.fs" />
     <Compile Include="FSharp.Core\PrimTypes.fs" />
     <Compile Include="FSharp.Core\ComparersRegression.fs" />
@@ -95,21 +95,13 @@
     <Compile Include="SurfaceArea.fs" />
   </ItemGroup>
 
-  <ItemGroup />
-
-  <ItemGroup Condition="'$(BUILD_IN_FSHARP_REPOSITORY)' == 'true'">
-    <ProjectReference Include="$(FSharpSourcesRoot)\fsharp\FSharp.Core\FSharp.Core.fsproj" />
-    <PackageReference Include="FsCheck" Version="$(FsCheckVersion)" />
+  <ItemGroup>
+    <Content Include="xunit.runner.json" CopyToOutputDirectory="PreserveNewest" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(BUILD_IN_FSHARP_REPOSITORY)' != 'true'">
-   <PackageReference Include="FSharp.Core" Version="4.6.0" />
-   <PackageReference Include="FsCheck" Version="3.0.0-alpha4" />
- </ItemGroup>
 
-  <ItemGroup Condition="'$(UnitTestType)' == 'xunit'">
-    <PackageReference Include="xunit" Version="2.4.1" PrivateAssets="All" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1" PrivateAssets="All" />
+  <ItemGroup>
+    <ProjectReference Include="$(FSharpSourcesRoot)\fsharp\FSharp.Core\FSharp.Core.fsproj" />
+    <PackageReference Include="FsCheck" Version="$(FsCheckVersion)" />
   </ItemGroup>
-
 </Project>