<PackageReference Include="NUnit" Version="4.3.0" />

PrefixOperator

public abstract class PrefixOperator : ConstraintOperator
PrefixOperator takes a single constraint and modifies its action in some way.
using System.Runtime.CompilerServices; namespace NUnit.Framework.Constraints { [NullableContext(1)] [Nullable(0)] public abstract class PrefixOperator : ConstraintOperator { public override void Reduce(ConstraintBuilder.ConstraintStack stack) { stack.Push(ApplyPrefix(stack.Pop())); } public abstract IConstraint ApplyPrefix(IConstraint constraint); } }