Domain Testing: Divide and Conquer - Testing Education

Hutcheson (2003) described boundary value analysis as one of the most
important testing techniques. “Boundary value analysis is a test data selection
technique in which values are chosen to lie along data extremes. Boundary values
include maximum, minimum, just inside and outside boundaries, typical values,
and error values” (p. 316).
Those who practice boundary value analysis believe that areas on the
boundary and around it are risky areas. This, in fact, is a risk-based strategy.
According to Kaner et al. (2002), in boundary testing the values of an equivalence
class are mapped onto a number line and the boundary values, which are the
extreme endpoints of the mapping and the values just beyond the boundaries, are
chosen as the best representatives of that equivalence class. “A best representative
of an equivalence class is a value that is at least as likely as any other value in the
class to expose an error in the software” (p. 37).
Kaner et al. (1999) depicted different kinds of boundaries, some of which
are described below.
• Numeric boundaries: lower and upper boundaries defined by a range of
values or a single boundary defined by equality.
• Boundaries on numerosity: boundaries defined by the length (or ranges
of length) of the elements or the number of constituent characters in the
elements.
• Boundaries in loops: minimum and maximum number of times a loop
can execute will determine the lower and upper boundaries,
respectively, for the loop iterations.
• Boundaries within data structures: boundaries defined by the lower and
upper bounds of structures that store data.
• Boundaries in space: boundaries defined by the bounds of objects in
two-dimensional or three-dimensional space.
• Boundaries in time: boundaries defined by time-determined tasks.
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