What major incident investigations teach us about inputs, interfaces, deployment, performance, timing, and recovery.

A successful test tells us something specific: under the conditions we exercised, the system satisfied the assertions we checked. Major failures often reveal the boundary of that evidence.

The eight incidents below offer concrete ways to strengthen it. Their published investigations document technical defects alongside gaps in validation, release processes, design, and operations. The proposed tests are an engineering interpretation of those findings, not a claim that a QA team alone could guarantee prevention.

Each illustration separates the failure mechanism from controls that could detect the defect or reduce its impact.

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