appendix 1. analyzing the triangle problem - Testing Education

ANALYZING THE TRIANGLE PROBLEM
“No book on software testing is complete without a discussion of the triangle problem.” Ed Kit.
(This is meant as a joke, because this problem has been thoroughly worked and re-worked over
the years. Nevertheless, this problem still retains its educational value.)
At least six self-proclaimed experts have developed answers for the triangle problem (including
this self-proclaimed expert, the author), and each answer is different. When experts do not agree
on the answer to a seemingly simple problem, perhaps this tells us something about the state of
the art of testing.
The triangle problem was mentioned in Chapter III. Using intuitive, off-the-cuff techniques,
systems professionals were able to identify only about half the test cases for the triangle problem.
This problem provides an opportunity to see how the functional analysis, path analysis, boundary
value and risk assessment methods can be applied.
Re-Statement of the Problem
Develop a set of test cases to adequately test a program, which works as follows:
The program reads three input numbers that represent the lengths of the three sides of a
triangle.
Based on these three input values, the program determines whether the triangle is scalene
(that is, it has three unequal sides), isosceles (two equal sides), or equilateral (three equal
sides).
The program displays the result on the screen.
Glen Meyers originally described this problem in his book, “The Art of Software Testing”.
Exercise (Allow 15 to 20 minutes for this exercise.)
There is no one correct theoretical answer to any testing problem. The answer depends on the
assumptions and judgement calls which the test planner makes.
Review and critique the following set of test cases for the triangle problem. How do you suggest
that we improve them?
Copyright 2004 Collard 2 & Company
Appendix 1
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