This application discloses a computing system implementing an automatic test pattern generation tool to convert a transistor-level model of a library cell describing a digital circuit into a switch-level model of the library cell, generate test patterns configured to enable detection of target defects injected into the switch-level model of the library cell, and bifurcate the test patterns into a first subset of the test patterns and a second set of the test patterns based on detection types for the target defects enabled by the test patterns. The computing system can implement a cell model generation tool to perform an analog simulation of the transistor-level model of the library cell using the second subset of the test patterns to verify that they enable detection of target defects, while skipping performance of the analog simulation of the transistor-level model of the library cell using the first subset of the test patterns.