Polyfill.NUnit 1.0.0

Polyfill.NUnit

Purpose

Polyfill.NUnit lets you cross-target legacy frameworks (e.g. netstandard2.0, netcoreapp3.1, net5.0) while beginning to use selected features that NUnit 4 introduces. NUnit 4 raises its minimum supported target frameworks and will never support net5.0, so this library provides a transitional window: Keep older TFMs in your multi-target matrix for maintenance while adopting newer, more expressive NUnit syntax.

What it provides

Focused, source-compatible polyfills that mimic NUnit 4 surface area where:

• The API is additive (safe forward removal once you move fully to NUnit 4)
• Behavior can match existing NUnit 4 functionality exactly, but does not guarantee it
• NUnit analyzers (and general modernization efforts) encourage newer syntax (e.g. collection expressions) that would otherwise not compile on NUnit 3

Currently included:

• Is.EqualTo<T>(T[]) generic array overload on Is, enabling collection expression usage: Is.EqualTo([1, 2, 3]).
• Is.EquivalentTo<T>(T[]) generic array overload on Is, enabling collection expression usage: Is.EquivalentTo([1, 2, 3]).
• using (Assert.EnterMultipleScope()) for multiple assertion scopes, superseding Assert.Multiple.

Requirements

The test project must use at least C# 14 for the new extensions feature.

Example

Use NUnit 4 like you usually would, even on legacy target frameworks!

using NUnit.Framework;

[TestFixture]
public class SampleTests
{
    [Test]
    public void ArrayEquality_UsesPolyfilledOverload()
    {
        var data = new[] { 1, 2, 3 };
        Assert.That(data, Is.EqualTo([1, 2, 3]));
    }
    
    [Test]
    public void ArrayEquivalence_UsesPolyfilledOverload()
    {
        var data = new[] { 1, 2, 3 };
        Assert.That(data, Is.EquivalentTo([1, 2, 3]));
    }

    [Test]
    public void MultipleAsserts_CanUseEnterMultipleScope()
    {
        var data = new[] { 1, 2, 3 };
        using (Assert.EnterMultipleScope())
        {
            Assert.That(data, Is.EqualTo([1, 2, 3]));
            Assert.That(data, Is.EquivalentTo([3, 2, 1]));
        }
    }
}

Setup

Include the Polyfill.NUnit NuGet package in your test project that targets legacy frameworks. This can either be done in the project file or a shared Directory.Build.props file.

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

  <PropertyGroup>
    <TargetFrameworks>netcoreapp3.1;net5.0;net10.0</TargetFrameworks>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="NUnit" Version="4.4.0" />
    
  </ItemGroup>

  <ItemGroup>
  </ItemGroup>

  
  <ItemGroup Condition="'$(TargetFramework)'=='net5.0' Or '$(TargetFramework)'=='netcoreapp3.1'">
    <PackageReference Update="NUnit" Version="3.14" />
    <PackageReference Include="Polyfill.NUnit" Version="1.0.0" />
  </ItemGroup>

</Project>

Credits

All credits for the original NUnit design, concepts, and implementation belongs to the NUnit team. This project is unaffiliated and purely a compatibility aid and is very much slightly adopted code from the original NUnit source.

https://github.com/nunit/nunit