Testing is intended to show that a program does what it is intended to do and to discover program defects before it is put into use. When you test software, you execute a program using artificial data. You check the results of the test run for errors, anomalies, or information about the programs non-functional attributes.
The testing process has two distinct goals:
1. To demonstrate to the developer and the customer that the software meets its requirements. For custom software, this means that there should be at least one test for every requirement in the requirements document. For generic software products, it means that there should be tests for all of the system features, plus combinations of these features, that will be incorporated in the product release.
2. To discover situations in which the behavior of the software is incorrect, undesirable, or does not conform to its specification. These are a consequence of software defects. Defect testing is concerned with rooting out undesirable system behavior such as system crashes, unwanted interactions with other systems, incorrect computations, and data corruption.
DEVELOPMENT TESTING:
Development testing includes all testing activities that are carried out by the team developing the system. The tester of the software is usually the programmer who developed that software, although this is not always the case. Some development processes use programmer/tester pairs where each programmer has an associated tester who develops tests and assists with the testing process. For critical systems, a more formal process may be used, with a separate testing group within the development team. They are responsible for developing tests and maintaining detailed records of test results. During development, testing may be carried out at three levels of granularity:
1. UNIT TESTING:
Unit testing is the process of testing program components, such as methods or object classes. Individual functions or methods are the simplest type of component. Your tests should be calls to these routines with different input parameters.. Unit testing should focus on testing the functionality of objects or methods.
When you are testing object classes, you should design your tests to provide coverage of all of the features of the object. This means that you should:
• Test all operations associated with the object.
• Set and check the value of all attributes associated with the object.
• Put the object into all possible states. This means that you should simulate all events that cause a state change.
2. COMPONENT TESTING:
Software components are often composite components that are made up of several interacting objects. For example, in the weather station system, the reconfiguration component includes objects that deal with each aspect of the reconfiguration. You access the functionality of these objects through the defined component interface. Testing composite components should therefore focus on showing that the component interface behaves according to its specification. You can assume that unit tests on the individual objects within the component have been completed. Assume that components A, B, and C have been integrated to create a larger component or subsystem. The test cases are not applied to the individual components but rather to the interface of the composite component created by combining these components. Interface errors in the composite component may not be detectable by testing the individual objects because these errors result from interactions between the objects in the component.
3. SYSTEM TESTING:
System testing during development involves integrating components to create a version of the system and then testing the integrated system. System testing checks that components are compatible interact correctly and transfer the right data at the right time across their interfaces. It obviously overlaps with component testing but there are two important differences:
(a) During system testing, reusable components that have been separately developed and off-the-shelf systems may be integrated with newly developed components. The complete system is then tested.
(b) Components developed by different team members or groups may be integrated at this stage. System testing is a collective rather than an individual process. In some companies, system testing may involve a separate testing team with no involvement from designers and programmers.
