Domain Testing: Divide and Conquer - Testing Education

• Hardware-related boundaries: boundaries defined by the upper and
lower bounds of hardware needs and requirements.
According to Hutcheson (2003), boundary value analysis is based on the
belief that if a system works correctly for the boundary values, it will also work
correctly for all the values within the range. This makes boundary values the most
important test cases.
Hutcheson (2003) explained that applying boundary value analysis to a
month variable will yield the following six test cases: {0, 1, 2, 11, 12, 13}. The test
cases or data points 1 and 12 are minimum and maximum values, respectively, that
a month variable can take. Test cases 0 and 2 are just outside and just inside the
boundary defined by test case 1, respectively. Similarly, test cases 11 and 13 are
just inside and just outside the boundary defined by test case 12, respectively.
Hutcheson (2003) further noted that test cases 2 and 11 seem redundant, as
both of these serve as data points from the region within the two endpoints. The
researcher therefore suggested replacing the two test cases 2 and 11 with mid-point
data value 6, which makes {0, 1, 6, 12, 13} the final set of test cases due to
boundary value analysis.
Some other researchers have not recommended using any values other than
those on the boundaries and ones that are just beyond the boundaries, since the
others would simply be redundant. According to them, in the aforementioned
example the test case 6 would also be redundant (Kaner et al., 2002; Kaner et al.,
1999; Kaner & Bach, 2003; Myers, 1979).
Jorgensen (2002) pointed out one outstanding disadvantage of boundary
value analysis. This analysis works well only when there are independent variables
that belong to domains with well-defined boundaries.
Jorgensen (2002) gave an example of a function that evaluates the next date
of the current date. Just applying boundary value analysis to the date variable of
this function will miss errors corresponding to that of a leap year. Also, boundary
value analysis cannot be applied to non-linearizable discrete variables.
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