public void UseCase_For_That() { var visitor = new Visitor { Programs = new[] { new Program { Name = "Some" }, new Program { Active = false }, } }; //Assert.IsTrue(visitor.Programs.Exists(p => p.Active), // "visitor should have at least one active program"); RuleAssert.That(() => visitor, v => v.Programs.Exists(p => p.Active), v => v.Programs.Length > 1); RuleAssert.That(visitor, v => v.Programs.Exists(p => p.Active), v => v.Programs.Length > 1); }