Methods, systems, and computer programs, for estimating think times. One of the methods includes receiving a request to perform a test of one or more computing resources. The test of the one or more computing resources is performed by simulating an interaction of one or more simulated users with the one or more computing resources. Requests are submitted from the simulated user for execution by the one or more computing resources. Respective response times of the one or more computing resources to each of the requests are measured. An estimated think time of the simulated user is computed, wherein the estimated think time is computed based on at least one preceding response time.