1. A method for updating a test description for an automated computer test, the automated test being configured, when executed, to cause a test computer system to communicate with a system under test comprising one or more computer programs being executed upon a computer device, wherein the test description is configured to be executed by a test program to cause the test computer system to perform an automated computer test by comparing a received image from a GUI of the system under test with one or more reference images to identify an expected image, wherein the method comprises: a) receiving a user input representative of the selection of at least one pixel of a desired reference image from a GUI of a system under test; and b) automatically obtaining the desired reference image by: c) identifying one or more correlations between the at least one selected pixel and one or more adjacent pixels of the GUI of the system under test to determine a group of pixels corresponding to the desired reference image; d) determining the image boundaries of the desired reference image based the determined group of pixels and/or any identified correlations; e) capturing the desired reference image delimited by the determined image boundaries; and f) updating the test description with the captured reference image.