<PackageReference Include="NUnit" Version="4.3.2" />

NUnit.Framework.Internal.ConstraintUtils

static class ConstraintUtils
Provides methods to support consistent checking in constraints.
namespace NUnit.Framework.Internal { internal static class ConstraintUtils { public static T RequireActual<[System.Runtime.CompilerServices.Nullable(2)] T>(object actual, string paramName, bool allowNull = false); } }