Model based development offers many advantages to developers of functionally safe and secure software. There are some caveats however, as highlighted (for example) by ISO 26262:2018 which suggests that "In comparison to a traditional development process where lifecycle data are separated, a stronger coalescence of the phases ... may occur. The potential benefits of this approach ... are appealing, but this approach may also introduce issues causing systematic faults". This overview presentation describes an approach to testing that is integrated with the modelling tool but at the same time is independent from it, helping to offset the concerns with regards to systemic failure.