<PackageReference Include="NUnit" Version="2.7.0" />

Does

public static class Does
Helper class with properties and methods that supply a number of constraints used in Asserts.
public static ConstraintExpression Not { get; }

Returns a ConstraintExpression that negates any following constraint.

public static SubstringConstraint 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.

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.