  A number of automated techniques and tools were proposed in the research
literature over the years which aim to support the spreadsheet developer in the
process of testing and debugging a faulty spreadsheet. One underlying
assumption of many of these approaches is that the spreadsheet developer is
capable of providing test cases or is at least reliably able to determine
whether a calculated value in a certain cell is correct given the current set
of inputs.
  Since real-world spreadsheets can be complex, we argue that these assumptions
might be too strong in some situations. We therefore propose to support the
user during testing and debugging by automatically computing spreadsheet
fragments of manageable size. The spreadsheet developer can then verify the
correctness of a smaller set of formulas for which the calculated output can be
more easily validated.
