1. Software products are normally tested first at the individual component level.
2. This is referred to as testing in the small.
3. After testing all the components individually, the components are slowly integrated and tested at each level of integration.
4. Finally, the fully integrated system is tested.
5. Integration and system testing are known as testing in the large.
6. Thus, a software product goes through three levels of testing,
1).Unit testing.
2).Integration testing.
3).System testing.
7. Unit testing usually refers to the process of testing the small unit or the entire system.
8. This process usually exposes the bugs, existing in the control paths located internal to a given unit.
9. Usually, the value and the uncovering of bugs using this process are low as the test is restricted to only a small component of the system.
10. The application of this test can be made to inspect the internal processing aspects of the component as well as its data structures.
11. Finally, unit testing can be carried out simultaneously on multiple units of the system.
12. Initially, consider the diagrammatic representation of various aspects of unit testing applied o a single component of the system.
13. The testing of interface ensures that there is free data movement into a given module.
14. This is the most essential aspect of the unit, hence, it is conducted prior to all.
15. It should be noted that the unit test cannot proceed further if it fails in testing the interface.
16. Testing of local data structures causes to verify that the integrity of temporarily stored data is not lost even during the complete execution of the component.
17. Testing the boundary conditions is important to verify that the component executes accurately been at its terminating line.
18. This is also one of the most essential aspects of the unit testing since there is a maximum probability of occurrence of errors at the component boundaries.
19. In this case, improper comparisons, erotic control flow, erotic computations are a few major causes for which test cases are generated.
20. Hence, if we proceed further in the testing independent paths the commonly encountered errors are tabulated in the table.
21. In general terms the word driver, in terms of software engineering terminology refers to a piece of code that takes est case input from one end passes this input to the software unit to be tested and displays the required output.