You’ve mapped out a client’s internal controls. Now the real question: do those controls actually work well enough to stop or catch big mistakes in the financial statements? This chapter shows you how auditors answer that question—how we judge if a control is designed right, test whether it runs reliably all year, and sort any problems we find. By the end, you’ll know exactly what it means when an auditor says a company has a “material weakness” and why that matters so much.