FITBOX - A Fault Isolation Toolbox★★Carlos Silvestre is on leave from Instituto Superior Técnico/University of Lisbon, 1049-001 Lisbon, Portugal. The work of Pedro Casau was partially supported by grants SFRH/BD/70656/2010 and the project PEst-OE/EEI/LA0009/2013 both from the Fundação para a Ciência e a Tecnologia. Research by Carlos Silvestre has been supported by projects MYRG118(Y1-L3)-FST12-SSW and MYRG117(Y1-L3)-FST12-MKM of the University of Macau.