无法使用FluentAssertions/Shouldly，添加包引用后仍遇问题

Hey there! Let's walk through why FluentAssertions and Shouldly aren't working for you, based on the package references you shared. Here are the most common fixes to try:

1. Verify Packages Are Properly Installed #

First, double-check that the NuGet packages actually installed successfully—sometimes restore operations fail silently:

• In Visual Studio, right-click your project → Manage NuGet Packages, then switch to the Installed tab to confirm FluentAssertions, Shouldly, and all test-related packages are listed with the versions you specified.
• If they're missing, run dotnet restore in your project's root directory, or use the NuGet Package Manager to reinstall them.

2. Add Required Namespace Usings #

This is the most frequent culprit! Both libraries require you to add their namespaces at the top of your test classes:

// For FluentAssertions
using FluentAssertions;

// For Shouldly
using Shouldly;

Without these, the extension methods (like Should() or ShouldBe()) won't show up in IntelliSense or compile.

3. Check .NET Version Compatibility #

Your package versions are quite outdated (FluentAssertions 4.19.0, Shouldly 3.0.0)—these older releases might not play well with newer .NET versions (like .NET 6/7/8).

Try upgrading to the latest stable versions of all your test packages to ensure compatibility. Here's an updated PackageReference block you can use:

<ItemGroup>
  <PackageReference Include="FluentAssertions" Version="6.12.0" />
  <PackageReference Include="nunit" Version="3.13.3" />
  <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
  <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
  <PackageReference Include="Moq" Version="4.20.70" />
  <PackageReference Include="Shouldly" Version="4.2.1" />
</ItemGroup>

4. Clean & Rebuild Your Project #

Cached build artifacts can sometimes cause weird reference issues. Try these steps:

• Right-click your project → Clean
• Delete the bin and obj folders from your project directory
• Right-click your project → Build (or Rebuild)

5. Test with a Minimal Project #

If none of the above works, create a brand new test project, add only the updated packages from step 3, and write a simple test to verify functionality:

using NUnit.Framework;
using FluentAssertions;
using Shouldly;

namespace MinimalTestProject
{
    public class BasicTests
    {
        [Test]
        public void TestFluentAssertionsWorks()
        {
            int actual = 42;
            actual.Should().Be(42);
        }

        [Test]
        public void TestShouldlyWorks()
        {
            int actual = 42;
            actual.ShouldBe(42);
        }
    }
}

If this minimal project works, your original project likely has a corrupted configuration or reference conflict. Compare the project files (.csproj) of the new and old projects to spot differences.

内容的提问来源于stack exchange，提问作者Mate