Debugging by Thinking

224 9.:3 Write a unit test

9.3

Read the control flow of a procedure or calling tree of the program

in a depth-first manner. Open a control-flow construct until it's

completely unfolded, and read the entire nested construct. Repeat

for each top-level nested construct, top to bottom, until done.

9 Use a class-hierarchy browser to do one of the following:

Review the inheritance hierarchy of the program in a breadth-first

manner. Open all the derived classes at the same nesting level,

review them top to bottom, and proceed to the next level until

done.

Read the inheritance hierarchy of the program in a depth-first

manner. Open a base class until it's completely unfolded, and

review the hierarchy. Repeat for each base class, top to bottom,

until done.

9 Use a word processor that supports underlining and multiple text col-

ors to read the text and apply one of the refined tactics to the pro-

gram text.

Write a unit test

9.3. I Basic tactic

Write a test that invokes a procedure in question and compares its result or

side effects with an expected result that is embedded in the test procedure.

9.3.2 Purpose

Determine whether a specific procedure is functioning as you expect it

should.

9.3.3

Questions answered

9 What inputs does a procedure accept?

9 What results does a procedure compute?

9 What side effects does a procedure cause?

9 What exceptions does a procedure activate?

9 What outputs does a procedure display?