An apparatus, computer-implemented method performed by a computerized device and a computer program product, the method comprising: receiving an attribute collection related to a domain, the attribute collection comprising two or more attributes; receiving one or more restrictions, each restriction indicating one or more attributes, wherein a value for the attribute is to be selected from one existing test; receiving an existing test; and generating one or more new tests by setting values for the two or more attributes, wherein values for the one or more attributes of the one or more restrictions are selected from the existing test, and one or more values for one or more other attributes are not selected from the existing test.