Yep. Think there was a discussion on this not too long ago in the Functional Testing forum. Do a search on "boundary" or "boundary value analysis" using the Search tool in the top right corner of your screen.
There's also an explanation of this in "Testing Computer Software" by Cem Kaner, et. al.
A great many errors happen at the boundaries of the input domain and for
this reason boundary value analysis was developed. Boundary value analysis
is test case design approach that complements equivalence partitioning. BVA
produces test cases from the output domain also.
Guidelines for BVA are close to those for equivalence partitioning:
· If an input condition specifies a range bounded by values a and b,
test cases should be produced with values a and b, just above and just below
a and b, respectively.
· If an input condition specifies various values, test cases should be
produced to exercise the minimum and maximum numbers.
· Apply guidelines above to output conditions.
· If internal program data structures have prescribed boundaries,
produce test cases to exercise that data structure at its boundary.