This accessible book examines issues such as test design, the rating process, validity, measurement, and the social dimension of language testing. It looks at both traditional and newer forms of language assessment, and the challenges posed by new views.
A DELTA Module 3 must-have, you'll need a reference or two from here & this short and readable handbook will get your head around assessment, the key terms, and concepts. For a star more I'd add Evaluating your Students by Andy Baxter which has a friendlier layout.
Relatively good for a broad overview (what the series is for), but it pales in comparison to Baxter's "Evaluate your students". McNamara also frequently makes use of tortured metaphors which does nothing to illuminate his subject.