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

NUnit.Framework.Does

public abstract class Does
Helper class with properties and methods that supply a number of constraints used in Asserts.
namespace NUnit.Framework { public abstract class Does { public static ConstraintExpression Not { get; } public static FileOrDirectoryExistsConstraint Exist { get; } public static SomeItemsConstraint Contain(object expected); public static ContainsConstraint Contain(string expected); public static DictionaryContainsKeyConstraint ContainKey(object expected); public static DictionaryContainsValueConstraint ContainValue(object expected); public static StartsWithConstraint StartWith(string expected); public static EndsWithConstraint EndWith(string expected); public static RegexConstraint Match(string pattern); public static RegexConstraint Match(Regex regex); protected Does(); } }