The three main assertion-based verification approaches are: Design by Contract (DBC), Extended Static Checking (ESC) and Verified Design by Contract (VDBC). Each approach offers a different balance between rigour and ease of use making them appropriate in different situations. Our goal is to explore the use of these approaches together in a flexible way, enabling an application to be broken down into sections with different reliability requirements and different verification approaches used in each section. We explain the benefits of using the approaches together, present a set of guidelines to avoid potential conflicts and give an overview of how the Omnibus IDE provides support for the full range of assertion-based verification approaches within a single tool.