A test executive sequence may be created by including a plurality of test executive steps in the test executive sequence and configuring at least a subset of the steps to call user-supplied code modules. One or more of the user-supplied code modules may take buffer parameters. The test executive sequence may be executed on a host computer under control of a test executive engine. When executing each step in the test executive sequence that calls a user-supplied code module that takes a buffer parameter, the test executive engine may be operable to perform several operations related to detecting a situation where the user-supplied code module writes outside the bounds of the buffer parameter and/or preventing the user-supplied code module from corrupting heap data if the user-supplied code module writes outside the bounds of the buffer parameter.