Volume III of the Handbook for Assessment in the Service of Learning bridges the gap between aspiration and application, by translating core design principles into practice through a collection of examples. This volume presents tangible "existence proofs" from a broad range of educational contexts—including digital learning platforms, PreK–12 classrooms, game-based learning environments, and skills-based credentialing programs. Each worked example can be understood through three complementary lenses: assessment as an evidentiary argument, as a feedback loop, and as a social practice. This framework reveals how thoughtfully designed assessment systems with actionable feedback can balance the need for evidence of learning. By showcasing assessments that are seamlessly integrated with learning and instruction, this volume advances the proposition that to assess is, fundamentally, to teach and to learn. It offers practical models and designs that embed assessment within instruction to cultivate skills and support meaningful learning.