Abstract: A functional behaviour test system for a target computer program includes data defining user interface functionality encoded in a data repository. The test functional behaviour system includes a definition system arranged to receive, for the target computer program, a selection of a functional behaviour test definition, the definition system further being arranged to receive an input on one or more parameters for the selected behaviour test definition to define a functional behaviour test for the target computer program, a validation system arranged to validate the functional behaviour test in dependence on the data defining user interface functionality, a data repository to store the validated functional behaviour test, and a test interface system to provide access by a substantially automated execution environment to the validated functional behaviour test in the data repository for testing of the validated functional behaviour test against the target computer program.