public void Equals_WithEqualityComponentsNull_ShouldThrow()
        {
            var    instance1 = new Dummy1();
            var    instance2 = new Dummy1();
            Action action    = () => instance1.Equals(instance2);

            action.ShouldThrow <InvalidOperationException>()
            .Message.ShouldBe("GetEqualityComponents must return at least one component.");
        }