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

NUnit.Framework.Constraints.ConstraintOperator

public abstract class ConstraintOperator
The ConstraintOperator class is used internally by a ConstraintBuilder to represent an operator that modifies or combines constraints. Constraint operators use left and right precedence values to determine whether the top operator on the stack should be reduced before pushing a new operator.
namespace NUnit.Framework.Constraints { public abstract class ConstraintOperator { protected int left_precedence; protected int right_precedence; public object LeftContext { get; set; } public object RightContext { get; set; } public virtual int LeftPrecedence { get; } public virtual int RightPrecedence { get; } public abstract void Reduce(ConstraintBuilder.ConstraintStack stack); protected ConstraintOperator(); } }