1. Testing
More In CS430

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
Testing

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
Testing

4. Software Life Cycle Costs
Requirement Analysis 3%
Specification 3%
Design %
Coding %
Testing %
Operation & Maintenance 67%
Testing

5. Cost of Finding & Fixing Software Errors
The sooner a bug is found & fixed, the cheaper
Cost
Requirements
Coded
Released
Testing

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.
Testing

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
Testing

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
Testing

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
Testing

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
Testing

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.
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
Testing

13. You cannot test a program completely
Myers, 1976, described a 100-line program that had 1018 unique paths.
Note that the universe is only 4x1017 seconds old!
Testing