Object-Oriented Design - Java Software Solutions: Foundations of Program Design - page 348

plus 1. Test cases that use these cases, plus at least one from within the general
field of the category, should be defined.
Let's look at an example. Consider a method whose purpose is to validate that
a particular integer value is in the range 0 to 99, inclusive. There are three equiva-
lence categories in this case: values below 0, values in the range of 0 to 99, and
values above 99. Black-box testing dictates that we use test values that surround
and fall on the boundaries, as well as some general values from the equivalence
categories. Therefore, a set of black-box test cases for this situation might be:
−500, −1, 0, 1, 50, 98, 99, 100, and 500.
White-box testing, also known as glass-box testing, exercises the internal struc-
ture and implementation of a method. A white-box test case is based on the logic
of the code. The goal is to ensure that every path through a program is executed at
least once. A white-box test maps the possible paths through the code and ensures
that the test cases cause every path to be executed. This type of testing is often
called statement coverage.
Paths through code are controlled by various control flow statements that
use conditional expressions, such as if statements. In order to have every path
through the program executed at least once, the input data values for the test
cases need to control the values for the conditional expressions. The input data of
one or more test cases should cause the condition of an if statement to evaluate
to true in at least one case and to false in at least one case. Covering both true
and false values in an if statement guarantees that both the paths through the if
statement will be executed. Similar situations can be created for loops and other
constructs.
In both black-box and white-box testing, the expected output for each test
should be established prior to running the test. It's too easy to be persuaded that
the results of a test are appropriate if you haven't first carefully determined what
the results should be.
SELF-REVIEW QUESTION (see answer in Appendix N)
SR 7.25 Select the term from the following list that best matches each of the
following phrases:
black-box, defects, regression, review, test case, test suite, walk-
through, white-box
a. Running previous test cases after a change is made to a program
to help ensure that the change did not introduce an error.
b. A meeting in which several people collectively evaluate an artifact.
c. A review that steps carefully through a document, evaluating each
section.
d. The goal of testing is to discover these.