SoftwareTesting

Software Testing

Observations about Testing
 “Testing is the process of executing a

program with the intention of finding errors.” – Myers
 “Testing can show the presence of bugs but never their absence.” - Dijkstra

Good Testing Practices
 A good test case is one that has a high

probability of detecting an undiscovered defect, not one that shows that the program works correctly
 It is impossible to test your own program
 A necessary part of every test case is a description of the expected result

Good Testing Practices
(cont’d)
 Avoid nonreproducible or on-the-fly testing
 Write test cases for valid as well as invalid

input conditions.
 Thoroughly inspect the results of each test
 As the number of detected defects in a piece of software increases, the probability of the existence of more undetected defects also increases

Good Testing Practices
(cont’d)
 Assign your best people to testing
 Ensure that testability is a key objective

in your software design
 Never alter the program to make testing easier  Testing, like almost every other activity, must start with objectives

Levels of Testing
 Unit Testing
 Integration Testing
 Validation Testing




Regression Testing
Alpha Testing
Beta Testing

 Acceptance Testing

Unit Testing
 Algorithms and logic
 Data structures (global and local)
 Interfaces
 Independent paths
 Boundary conditions
 Error handling

Why Integration Testing Is
Necessary
 One module can have an adverse effect

on another
 Subfunctions, when combined, may not produce the desired major function
 Individually acceptable imprecision in calculations may be magnified to unacceptable levels

Why Integration Testing Is
Necessary (cont’d)
 Interfacing errors not detected in unit

testing may appear
 Timing problems (in real-time systems) are not detectable by unit testing
 Resource contention problems are not detectable by unit testing

Top-Down Integration
1.

2.

The main control module is used as a
driver,