Chapter 8 Software Testing PDF

Chapter 8 – Software Testing Development testing User testing 30/10/2014 Chapter 8 Software Testing 1 Program testing 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 us...

Chapter 8 – Software Testing Development testing User testing 30/10/2014 Chapter 8 Software Testing 1 Program testing 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 program’s non-functional attributes. Can reveal the presence of errors NOT their absence. Testing is part of a more general verification and validation process, which also includes static validation techniques. 30/10/2014 Chapter 8 Software Testing 2 Program testing goals To demonstrate to the developer and the customer that the software meets its requirements. To discover situations in which the behavior of the software is incorrect, undesirable or does not conform to its specification. Defect testing is concerned with rooting out undesirable system behavior such as system crashes, unwanted interactions with other systems. 30/10/2014 Chapter 8 Software Testing 3 Testing process goals Validation testing To demonstrate to the developer and the system customer that the software meets its requirements A successful test shows that the system operates as intended. Defect testing To discover faults or defects in the software where its behavior is incorrect or not in conformance with its specification A successful test is a test that makes the system perform incorrectly and so exposes a defect in the system. 30/10/2014 Chapter 8 Software Testing 4 An input-output model of program testing 30/10/2014 Chapter 8 Software Testing 5 Verification vs validation Verification: "Are we building the product right”. The software should conform to its specification. Validation: "Are we building the right product”. The software should do what the user really requires. 30/10/2014 Chapter 8 Software Testing 6 Inspections and testing Software inspections Concerned with analysis of the static system representation to discover problems (static verification) Software testing Concerned with exercising and observing product behaviour (dynamic verification) The system is executed with test data and its operational behaviour is observed. 30/10/2014 Chapter 8 Software Testing 7 Inspections and testing 30/10/2014 Chapter 8 Software Testing 8 Software inspections These involve people examining the source representation with the aim of discovering anomalies and defects. Inspections not require execution of a system so may be used before implementation. They may be applied to any representation of the system (requirements, design,configuration data, test data, etc.). 30/10/2014 Chapter 8 Software Testing 9 Advantages of inspections During testing, errors can mask (hide) other errors. Because inspection is a static process, you don’t have to be concerned with interactions between errors. Incomplete versions of a system can be inspected without additional costs. As well as searching for program defects, an inspection can also consider broader quality attributes of a program, such as compliance with standards, portability and maintainability. 30/10/2014 Chapter 8 Software Testing 10 Inspections and testing Inspections and testing are complementary and not opposing verification techniques. Both should be used during the V & V process. Inspections can check conformance with a specification but not conformance with the customer’s real requirements. Inspections cannot check non-functional characteristics such as performance, usability, etc. 30/10/2014 Chapter 8 Software Testing 11 A model of the software testing process 30/10/2014 Chapter 8 Software Testing 12 Stages of testing Development testing, where the system is tested during development to discover bugs and defects. Release testing, where a separate testing team test a complete version of the system before it is released to users. User testing, where users or potential users of a system test the system in their own environment. 30/10/2014 Chapter 8 Software Testing 13 Development testing Development testing includes all testing activities that are carried out by the team developing the system. Unit testing, where individual program units or object classes are tested. Unit testing should focus on testing the functionality of objects or methods. Component testing, where several individual units are integrated to create composite components. Component testing should focus on testing component interfaces. System testing, where some or all of the components in a system are integrated and the system is tested as a whole. System testing should focus on testing component interactions. 30/10/2014 Chapter 8 Software Testing 14 General testing guidelines Choose inputs that force the system to generate all error messages Design inputs that cause input buffers to overflow Repeat the same input or series of inputs numerous times Force invalid outputs to be generated Force computation results to be too large or too small. 30/10/2014 Chapter 8 Software Testing 15 User testing User or customer testing is a stage in the testing process in which users or customers provide input and advice on system testing. 30/10/2014 Chapter 8 Software Testing 16 Types of user testing Alpha testing Users of the software work with the development team to test the software at the developer’s site. Beta testing A release of the software is made available to users to allow them to experiment and to raise problems that they discover with the system developers. Acceptance testing Customers test a system to decide whether or not it is ready to be accepted from the system developers and deployed in the customer environment. Primarily for custom systems. 30/10/2014 Chapter 8 Software Testing 17 The acceptance testing process 30/10/2014 Chapter 8 Software Testing 18 Key points Testing can only show the presence of errors in a program. It cannot demonstrate that there are no remaining faults. Development testing is the responsibility of the software development team. A separate team should be responsible for testing a system before it is released to customers. User testing 30/10/2014 Chapter 8 Software Testing 19