1. A software testing method, comprising: training a programmatically implemented image classifier to recognize a screen shot image as being associated with a transaction end condition of a transaction; running a test script configured to initiate an iteration of the transaction; recording a start time of the iteration of the transaction; causing screen shot images to be generated during performance of the iteration of the transaction to capture a series of screen shot images of at least a portion of a user interface display associated with the iteration of the transaction; using the image classifier to find an earliest-captured image that matches the transaction end condition; and using a time associated with the matched image as a transaction end time to compute an end-to-end time to perform the iteration of the transaction.