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Testing

This text discusses the importance of testing and verification in ensuring that a program conforms to its specification. It explores techniques for verifying large programs and the challenges of testing all possible inputs. The example of testing fonts is used to illustrate the time-consuming nature of thorough verification. It also provides suggestions for effective testing and tools that can be used for automation. Additionally, it touches on the difficulties of testing GUIs and the benefits of scripting languages in testing.

franciscophelps
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Testing

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  1. Testing • Verification: Does the program conform to its specification? • How do you verify a large program? • $ Infinite Matrix of possibilities. • Can check a program conforms given a single input. • If have an input of all integers can’t possibly test all possible inputs.

  2. Example – Fonts • There are TrueType and Postscript fonts. • Each font can be 20 different sizes. • Each font can represent approximately 70 characters • There are hundreds of TrueType and Postscript fonts. • Verifying the display characteristics of each font and size would take a tremendous amount of time

  3. How can you Gain Confidence that Program meets specification? • Group similar objects together • Test a few similar objects extensively • Take a small sample of the rest

  4. Fonts Solution • Rigorously test 1 or 2 TrueType and 1 or 2 Postscript fonts with all sizes • Assume that every TrueType font is rather similar. • Test a small sample like 10 letters at 1 font size for the others.

  5. Suggestions for Assignment 4 • Skim, Do not read html specification • Search the web quickly for information related to this topic. Don’t replicate work when it already exists • Answer the easy questions first • Partition tags into related groups. • Only test hot spots • Do not forget the big picture. (You cannot afford to spend a lot of time on small details)

  6. Tools for testing • Expect tool primarily for automating interactive command line applications such as telnet, ftp, passwd, fsck, rlogin, tip, etc. Expect is also useful for testing this kind of application. • Basic use consists of “sending” a request (just like a user would do) and “expecting” a response. • Expect is very powerful and easy to use • "Exploring Expect"(Pub:O'Reilly, ISBN 1-56592-090-2)

  7. Tools for testing II DejaGnu • DejaGnu is a framework for testing other programs. Its purpose is to provide a single front end for all tests. • The DejaGnu framework allows for a large number of small test cases to be written and incorporated into larger Test Suites. • Handles statistics gathering on tests. • Flexible enough to write tests for any type of program • DejaGnu's output is designed to be parsed by other filtering script, and it is also human readable.

  8. Testing GUIs • Testing GUIs is difficult!!! • Simulating random mouse clicks require specialized software • Many different kinds of users for GUI systems • Application should be able to survive unknowledgeable users • A solution is to have a wrapper for every menu item/button and invoke the functions according to a typical usage scenario • A good test is the “Monkey” test. How long can the program go without crashing with a “Monkey” hitting random buttons.

  9. Scripting • Tcl/Tk, Perl, Python, Lisp variants, JPython, TclBlend • Scripting is an excellent tool for testing. • Script languages are interpreted – you can peak and poke with functions in real time • Scripts are very fast to write and can flexibly exercise program functions • Powerful regular expression packages make determining results of tests easier • Loosely typed languages • Great for testing in Embedded environments

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