This research looks at how ideas about test validity have developed over time, focusing on both the UK and the US. It covers key theories behind what makes a test valid, alongside real-world approaches to proving test quality. 

The authors highlight that while traditional psychometric data, especially in the US, still plays a major role in how we judge test quality, there are other important sources of evidence that shouldn’t be overlooked. They stress the value of careful, thoughtful test design, and argue that input from different teams involved in test development also contributes to overall quality. 

One of the central ideas in the monograph is ‘impact by design’, the belief that the effects of a test (on individuals, groups, and society) should be a top priority from the start. This focus on impact helps shape better testing practices and stronger arguments for validity. 

The authors also emphasize the importance of thinking about different stakeholders – those affected by or using test results – and making sure that communication is clear and tailored to each audience. This makes the case for a test’s validity more persuasive and relevant. 

Finally, the research encourages professionals to share local case studies that show how these ideas work in real-world testing situations. These examples help bring the theory to life and show how evidence and reasoning come together to support high-quality testing programmes.