Problemas com projeto de teste/integração de unidade .NET 8

Estou tendo problemas ao tentar fazer testes de unidade/integração com o .NET 8 em um projeto (pequena API que funciona). Eu queria adicionar testes a ele para aprender, já que nunca os fiz, mas estou me deparando com algo que não consigo resolver.

Estrutura raiz do meu projeto: Controladores, DTOs, Migrações, Modelos, Repositório, Serviços, mais arquivos e a pasta criada para testes (WebApi.Tests/)

Adicionei a pasta WebApi.Tests dentro do projeto principal (não sei se essa é a prática correta), mas quando executo, recebo erros como atributos duplicados e pacotes ausentes, como Xunit, FactAttribute, Fact.

Os pacotes são instalados:

/DotNetProjects/WebApi/WebApi.Tests$ dotnet list package --outdated

The following sources were used:
   https://api.nuget.org/v3/index.json

Project `WebApi.Tests` has the following updates to its packages
   [net8.0]: 
   Top-level Package                    Requested   Resolved   Latest 
   > coverlet.collector                 6.0.0       6.0.0      6.0.4  
   > Microsoft.NET.Test.Sdk             17.6.0      17.6.0     17.13.0
   > xunit                              2.6.3       2.6.3      2.9.3  
   > xunit.core                         2.6.3       2.6.3      2.9.3  
   > xunit.extensibility.core           2.6.3       2.6.3      2.9.3  
   > xunit.extensibility.execution      2.6.3       2.6.3      2.9.3  
   > xunit.runner.visualstudio          2.4.5       2.4.5      3.0.2

O mais estranho é que se eu executar meu projeto de teste sem a referência ao programa principal, consigo executar os testes sem problemas, porém quando adiciono a referência, recebo os erros: erros ao executar o teste dotnet:

DotNetProjects/WebApi/WebApi.Tests$ dotnet test 
  Determining projects to restore...
  All projects are up-to-date for restore.
/home/gustavo.ruiz/DotNetProjects/WebApi/obj/Debug/net8.0/.NETCoreApp,Version=v8.0.AssemblyAttributes.cs(4,12): error CS0579: Duplicate 'global::System.Runtime.Versioning.TargetFrameworkAttribute' attribute [/home/gustavo.ruiz/DotNetProjects/WebApi/WebApi.csproj]
/home/gustavo.ruiz/DotNetProjects/WebApi/WebApi.Tests/GlobalUsings.cs(1,14): error CS0246: The type or namespace name 'Xunit' could not be found (are you missing a using directive or an assembly reference?) [/home/gustavo.ruiz/DotNetProjects/WebApi/WebApi.csproj]
/home/gustavo.ruiz/DotNetProjects/WebApi/WebApi.Tests/UnitTest1.cs(5,6): error CS0246: The type or namespace name 'FactAttribute' could not be found (are you missing a using directive or an assembly reference?) [/home/gustavo.ruiz/DotNetProjects/WebApi/WebApi.csproj]
/home/gustavo.ruiz/DotNetProjects/WebApi/WebApi.Tests/UnitTest1.cs(5,6): error CS0246: The type or namespace name 'Fact' could not be found (are you missing a using directive or an assembly reference?) [/home/gustavo.ruiz/DotNetProjects/WebApi/WebApi.csproj]

WebApi.csproj:

<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
    <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="AutoMapper.Extensions.Microsoft.DependencyInjection" Version="12.0.1" />
    <PackageReference Include="FluentValidation" Version="11.11.0" />
    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="8.0.11" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="8.0.3" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.tools" Version="8.0.3">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
    <PackageReference Include="Swashbuckle.AspNetCore" Version="6.6.2" />
  </ItemGroup>
  <!-- <ItemGroup>
    <Compile Include="Services.fs" />
  </ItemGroup> -->
</Project>

WebApi.Testes.csproj:

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

  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>

    <IsPackable>false</IsPackable>
    <IsTestProject>true</IsTestProject>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.6.0" />
    <PackageReference Include="xunit" Version="2.6.3" />
    <PackageReference Include="xunit.core" Version="2.6.3" />
    <PackageReference Include="xunit.extensibility.core" Version="2.6.3" />
    <PackageReference Include="xunit.extensibility.execution" Version="2.6.3" />
    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
    <PackageReference Include="coverlet.collector" Version="6.0.0">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
  </ItemGroup>

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

</Project>

como comentei ao remover o ProjectReference isso executa os testes sem nenhum problema (embora ele praticamente só tenha criado o projeto de teste e tenha um código de exemplo)

UnitTest1.cs:

namespace WebApi.Tests;

public class UnitTest1
{
    [Fact]
    public void Test1()
    {
        Assert.True(true);
    }
}

Coisas que tentei:

• Exclua o projeto e recrie-o (dotnet new xunit -n WebApi.Tests -o WebApi.Tests)
• Exclua os diretórios bin e obj e execute dotnet restore, dotnet clean, dotnet build
• Reinstale os pacotes de teste

Gostaria de poder executar os testes sem erros