Module 1, part 7. Specifications, testing, and debugging
Introduction
Part 7 is about testing. But before one can test, one has to know what to test for —one has to know what a method or class to be tested is supposed to do. So, we discuss briefly the specifications of methods, fields of a class, and the class itself.
Since you have programmed before, you will know much of what we say here already, but a review won't hurt, especially of a topic as important as testing and debugging. Also, the use of a JUnit tester will probably be new to you.
Contents
| No. | Topic | Discussion |
|---|---|---|
| 1. | Specifications of methods. (blecture doc ppt.pdf) Reading: Gries/Gries, Sec.13.3.1, pp. 376–378. |
Each method should have a precise specification, indicating (1) constraints on calls of the method and (2) what the method does. |
| 2. | Assertions in programs. All 3 lectures on p. 1-6 of the ProgramLive CD. |
An assertion is a true-false statement about the program variables that is placed somewhere in a program. By placing it in before or after a statement, one asserts that the assertion is true at that point. |
| 3. | Javadoc specifications. (blecture doc) Reading: Gries/Gries, App. II.2, pp. 496–497; App. I.2.3, p. 486. |
Comments of a certain form, beginning with /**, will be extracted and put on a web page. This allows the user to look at the specs without having to look at the Java program. |
| 4. | Testing. (html) |
Testing is the process of running a program against "test cases" in order to get some evidence of the program's correctness. If a test case reveals an error, debugging (see points 6–7 below) takes place to find and correct the error. |
| 5. | JUnit testing. (blecture doc) |
DrJava provides a simple means for saving suites of test cases and executing them at will. |
| 6. | Debugging (introduction). (html) |
If an error has been detected, it must be found and removed. This is called debugging. |
| 7. | A demonstration of debugging. Watch the two lectures on p. 14-4 of the ProgramLive CD (feedback) |
We give some pointers on inserting print statements and demonstrate how to find a bug. |
| Reading material for testing and debugging: | Chapter 14 of Gries/Gries, pp. 385–401, is devoted to testing
and debugging. If your previous course did not teach you much about
these topics, read this chapter carefully. Sec. 14.1 discusses the process of testing; Sec. 14.2, approaches to creating test cases; Sec. 14.4, Java's assert statement, which can be useful in debugging; and Sec. 14.5, debugging itself. Gries/Gries, and App. I.2.4, pp. 486–489, covers JUnit testing in DrJava. The ProgramLive CD, pp. 14–1 through 14–4 are especially useful. |