<PackageReference Include="NUnit" Version="3.4.0" />

Does

public static class Does
Helper class with properties and methods that supply a number of constraints used in Asserts.
public static FileOrDirectoryExistsConstraint Exist { get; }

Returns a constraint that succeeds if the value is a file or directory and it exists.

public static ConstraintExpression Not { get; }

Returns a ConstraintExpression that negates any following constraint.

public static CollectionContainsConstraint Contain(object expected)

Returns a new CollectionContainsConstraint checking for the presence of a particular object in the collection.

public static ContainsConstraint Contain(string expected)

Returns a new ContainsConstraint. This constraint will, in turn, make use of the appropriate second-level constraint, depending on the type of the actual argument. This overload is only used if the item sought is a string, since any other type implies that we are looking for a collection member.

public static EndsWithConstraint EndWith(string expected)

Returns a constraint that succeeds if the actual value ends with the substring supplied as an argument.

public static RegexConstraint Match(string pattern)

Returns a constraint that succeeds if the actual value matches the regular expression supplied as an argument.

public static StartsWithConstraint StartWith(string expected)

Returns a constraint that succeeds if the actual value starts with the substring supplied as an argument.