How can assessment shed light on learners’ current abilities and help chart a path for their continued development? Dynamic assessment and diagnostic language assessment are both now well established in the second language (L2) field, and while they emerge from different theoretical traditions, they share a commitment to pursuing this question. The chapters in this volume showcase innovative work in both approaches undertaken by leading scholars around the world. Each chapter also offers insight into the complementary nature of the approaches, ultimately raising the possibility of how they might together form a powerful new assessment framework.