CSCI-1200 Computer Science II — Spring 2006
Lab 4 — Testing and Debugging
Testing and debugging are important steps in programming. Loosely, you can think of testing as verifying
that your program works and debugging as finding and fixing errors once you’ve discovered it does not.
Writing test code is an important (and sometimes tedious) step. Many software libraries have “regression
tests” that run automatically to verify that code is behaving the way it should. Here are four strategies for
testing and debugging:
1. When you write a class, write a separate “driver” main function that calls each member function,
providing input that produces a known, correct result. Output of the actual result or, better yet,
automatic comparison between actual and correct result allows for verifying the correctness of a class
and its member functions.
2. Carefully reading the code. In doing so, you must strive to read what the code actually says and does
rather than what you think and hope it will do. Although developing this skill isn’t necessarily easy,
it is important.
3. Judicious use of cout statements to see what the program is actually doing (a.k.a. “printf debug-
ging”). This is especially useful for printing the contents of a large data structure or class. It is often
hard to visualize large objects using the debugger (see next item) alone.
4. Using the debugger to (a) step through your program, (b) check the contents of various variables, and
(c) locate floating point exceptions and segmentation violations that cause your program to crash.
Points and Rectangles
The programming context for this lab is the problem of determining what 2D points are in what 2D rect-
angles. For rectangles, we will assume they are aligned with the coordinate axes (a.k.a. axis-aligned). This
makes it easy to represent and to test if a point is inside. Our code will create points and rectangles and
determine which points are in which rectangles. This type of problem is common in graphics and robotics.
The rectangle below is specified by its upper right corner point, (17,9), and its lower left corner point, (4,3).
The point (9,3.5) is inside the rectangle, whereas the point (8,10) is outside.
y
x
(4,3)
(17,9)
(9,3.5)
(8,10)
Please download the following 3 files needed for this lab and then turn off your internet connection:
http://www.cs.rpi.edu/academics/courses/spring06/cs2/labs/04_debugging/point2D.h
http://www.cs.rpi.edu/academics/courses/spring06/cs2/labs/04_debugging/rectangle.h
http://www.cs.rpi.edu/academics/courses/spring06/cs2/labs/04_debugging/rectangle.cpp
Checkpoint 1
Start by creating a project and adding the files Point2D.h,Rectangle.h, and Rectangle.cpp. Exam-
ine these files briefly. Point2D.h has a simple, self-contained class for representing point coordinates in
