You would first make sure the sensor is fully warmed up. Then let the engine idle until O2 is cycling. Then perform a WOT snap throttle. The initial gulp of air will drive the O2 max lean and then the accel fuel dump will drive it max rich. The lean level should be <100mv and the max level >800mv. 80% or so of the lean to rich switch here should occur in <100ms.
This only means that the O2 is OK at the time of testing. Intermittent issues are common.
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