A categorisation of testing in product design and development

Journal article, 2026

Testing is often narrowly viewed in the context of verification and validation in product design and development. However, testing also plays a critical role in product design, especially in the early stages, for exploration, experimentation and evaluation. While agile and set-based design emphasise iterative testing, these approaches do not fully address testing purposes across stages or consider diverse stakeholder needs. Empirical studies examining the multifaceted roles of testing throughout the design process are scarce in the academic literature. This paper fills this gap by presenting two detailed case studies on engine design and space propulsion systems, covering both incremental and radical product development in large-scale manufacturing settings. The findings show how testing purposes evolve with design progress and increasing specificity. Drawing on insights from the case studies and a review of the existing literature, the paper develops a systematic categorisation of the purposes of testing across design and development stages. This provides a foundation for a shared understanding among diverse stakeholders to support the effective use of testing in practice and offers consistent terminology to connect the academic literature on testing.