A test component and method of operation thereof are provided, the test component being arranged in a test environment to issue a test sequence over a bus to a device under test. A configuration file is provided to specify the behaviour of the test component, the configuration file comprising a plurality of regions with each region specifying attributes for use in determining the test sequence. The method of the present invention comprises the steps of: (a) when a test sequence is required to be issued, causing the test component to select, based on predetermined criteria, one of a number of regions provided by the configuration file; and (b) using the constraint attributes for that selected region to generate the test sequence to be issued on to the bus.