This paper considers transient response testing of amended analogue macros in mixed-signal systems. The stimulus employed for transient response testing is a single logic amplitude pulse which can be propagated through a digital interface scan path. However, the resulting response must either be readily accessible for processing at a primary output or somewhere routed off-chip. For a number of reasons this is usually considered impractical. This paper therefore considers the effects of sampling and quantising transient responses and extracting them through a digital scan path. The aim of this work is then to define a confidence limit in the accuracy of the test measurements obtained as a function of the number of samples taken, the resolution of the quantifier and the quantiser capture range.