1 Testing

2 About Testing  The reason the program is in testing is that it probably doesn’t work!  We test to find bugs before our users and hope that the developers will fix them  A test that reveals a problem is a successful one

3 Define “Bug”  A bug, or defect, in software is something that cause the software to behave in a manner that is inconsistent with the requirements or the needs of customers

4 Software Life Cycle Costs  Requirement Analysis3%  Specification3%  Design 5%  Coding7%  Testing 15%  Operation & Maintenance67%

5 Cost of Finding & Fixing Software Errors RequirementsCodedReleased Cost The sooner a bug is found & fixed, the cheaper

6 High Quality Software  One measure of the quality of software is delivered defect density -- the number of defects per unit size in the delivered software.

7 Quality Control V.S. Quality Assurance  Quality control focuses on finding (through testing and reviewing) and removing defects.  Quality Assurance is to verify that applicable procedures and standards are followed so the software’s quality is somewhat controlled

8 When Defects Are Introduced  Defect can be introduced during Requirement specification Design both high level and detailed Coding Bug fixing  Why? Software development is a highly people oriented activity and hence error-prone

9 Activities for Defect Removal  Are: Requirement reviews Code reviews (walk through) Unit testing Integration testing system testing  alpha test -- within the team  beta -- out side the team Acceptance test

10 You Can NOT find all the bugs  No matter how careful and thorough a job you do, you will never find the last bug in a program  Or if you do, you won’t know it

11 Some Wrong Concepts  We can fully test a program  With testing, we can ensure the correctness of a program  The tester’s mission is to assure program correctness by doing a complete testing.

12 You cannot test a program completely  Reason: The domain of possible input is too large to test There are too many possible paths through the program to test The user interface issue are too complex to completely test

13 You cannot test a program completely  Myers, 1976, described a 100-line program that had unique paths.  Note that the universe is only 4x10 17 seconds old!

14 Test Plan  Emphasize on testing the code Testing on different platforms, hardware configurations, with other software, other resource limitations Cover every use case Consists of test cases and schedule

15 Testing Phases  Basically there are two main phases By developers By independent testing teams

16 Testing Process Design Test Cases Prepare Test data Run a test Compare result Test casesTest DataTest ResultTest Report

17 Different Types of Tests  Black-box testing Equivalence partitioning  White-box testing (glass-box, clear-box)  Path test  Line test  Data test

18 Different Types of Tests  Integration Testing Top-down Bottom-up  Interface testing  Stress testing  Alpha test  Beta test  Acceptance test