<PackageReference Include="NUnit" Version="4.2.2" />

NUnit.Framework.Constraints.ContainsConstraint

ContainsConstraint tests a whether a string contains a substring or a collection contains an object. It postpones the decision of which test to use until the type of the actual argument is known. This allows testing whether a string is contained in a collection or as a substring of another string using the same syntax.
namespace NUnit.Framework.Constraints { public class ContainsConstraint : Constraint { public ContainsConstraint IgnoreCase { get; } public ContainsConstraint IgnoreWhiteSpace { get; } public ContainsConstraint(object expected); } }