Presentation on theme: "Unit-V -SOFTWARE QUALITY. To develop and deliver robust system, we need a high level of confidence that Each component will behave correctly Collective."— Presentation transcript:
Unit-V -SOFTWARE QUALITY
To develop and deliver robust system, we need a high level of confidence that Each component will behave correctly Collective behavior is correct No incorrect collective behavior will be produced Debugging and testing Quality assurance test, testing strategies, OO on Software quality, test plan and test cases.
Reason why quality assurance is needed, Computers are infamous for doing what we tell them to do, not necessarily what we want them to do. To close this gap, code must be free of errors or bugs that cause unexpected results
Software debugging system can provide tools for finding errors in programs and correcting them Different kinds of errors are Syntax errors Run-Time errors Logic errors
Quality assurance testing can be divided into two major categories Error based testing (testing the boundary condition) Scenario based testing (Usage-based testing) Error based Testing Search a given classs method for particular clues of interests, then describe how these clues should be tested Scenario based Testing Concentrates on what the user does, not what the product does
Extend of testing a system is controlled by many factors, such as the risks involved, limitations on resources and deadlines There are many test strategies, but most testing uses a combination of them Black box testing White box testing Top-Down testing Bottom-Up testing
Black Box Testing Used to represent a system whose inside workings are not available for inspection. Test items are tested as Black, since its logic is unknown, all that is known is what goes in and what comes out, i.e. input and output Works nicely in testing objects in OO environment
Black Box Testing Input Output
White Box Testing Assumes that the specific logic is important and must be tested to guarantee the systems proper functioning. Main use is in error-based testing, when we already have tested all objects of an application and all external or public methods of an object that are of greater importance One form of white box testing, called path testing, makes certain that each path in a objects method is executed at least once during testing.
Two types of path testing are Statement based testing Branch based testing
Top-Down Testing It assumes that the main logic or object interactions and systems message of the application need more testing than an individual objects method or supporting logic It can detect the design flows early in the implementation It supports testing the user interface and event-driven systems
Top-Down Testing It can test the navigation through screens and verify that it matches the requirement, users can see, at an early stage, how the final application will look and feel. Useful for Scenario-based testing. Useful to test subsystem and system integration.
Bottom-Up testing Starts with the details of the system and proceeds to higher levels by a progressive aggregation of details until they collectively for the requirements for the system. This approach is more appropriate for testing the individual object in a system. Test each object, combine them and test their interaction and the message passed among object by utilizing the top-down approach.
Bottom-Up testing In bottom-up, start with methods and classes that call or rely on no others, then progress to next level up. Those methods and classes that use only the bottom level ones already tested It leads to integration testing which leads to system testing
To have a comprehensive testing scheme, the test must cover all methods or a good majority of them. All services of the system should be checked atleast once. To test a system, given input and received output checked with expected output
The main objectives of testing are: Testing is the process of executing a program with the intent of finding errors. A good test case is the one that has a high probability of detecting an as-yet undiscovered error.
A test case is a set of what-if questions Thomas has developed guidelines that have been adapted for the UA Describe which feature or service your test attempts to cover If the test case is based on a use-case, it is good idea to refer to the use-case name. Use- cases are the source of test cases. Specify what you are testing and which particular feature Test the normal use of the objects methods.
Test the abnormal but reasonable use of objects method. Test the boundary condition Test objects interactions and message sent among them The internal quality of the software, such as reusability and extendibility should be assessed as well.
Test plan is developed to detect and identify potential problems before delivering the software to its users It provides the roadmap for testing activities, whether usability, user satisfaction or quality assurance tests.
Steps needed to create a test plan: Objectives of the test Development of a test case Test analysis All passed tests should be reported with the revised program called regression testing, which can discover errors introduced during the debugging process
For a small application, the designer or the design team usually will develop the test plan and test cases and in some situations, actually will perform the tests. Many organizations have a separate team, such as a quality assurance group, that works closely with the design team and is responsible for these activities
Most software companies also use beta testing a popular inexpensive and effective way to test software on a select group of the actual users of the system In contrast, alpha testing is done by in- house testers, such as programmers, software engineering and internal users.
You may have requirements that dictate a specific appearance or format for your test plan. Test plan should contain a schedule and a list of required resources After you have determined what types of testing are necessary, you need to document specifically what you are going to do
A configuration control system provides a way of tracking the changes to the code. A well thought out design tends to produce better code and result in more complete testing, so it is a good idea to buy to keep the plan up to date. At the end of each month, take time to complete routine updates.
Software is tested to determine whether it conforms to the specifications of requirements. Software is maintained when errors are found and corrected and software is extended when new functionality is added to an already existing program. There are different reasons for testing such as to test for potential problems in a proposed design or to compare two or more designs to determine which is better, given a specific task or set of tasks
Testing the whole system and detecting bugs is more difficult than testing smaller pieces of the application as it is being developed. Testing must take place on a continuous basis and this refining cycle must continue through out the development process until we are satisfied with the results.
The steps to successful testing: Understand and communicate the business case for improved testing Develop an internal infrastructure to support continuous testing. Look for leaders who will commit to and own the process Measures and document your findings in a defect recording system Publicize improvements as they are made and let people know what they are doing better
Bug Locating Principle: Think If you reach an impasse, sleep on it. If the impasse remains, describe the problem to someone else Use debugging tools Experimentation should be done as a last
Debugging Principle: Where there is a one bug, there is likely to be another Fix the error, not just the symptom of it The probability of the solution being correct drops as the size of the program increases Because of the possibility that an error correction will create a new error
What is testing ? List out the different testing strategies. What is black box testing? When would you use white box testing? If you dont know what is inside the box, how would you test it? What is the importance of developing a test case? What is white box testing? What is path testing? What is statement testing coverage? What is branch testing coverage? What is regression testing? What is a test plan? What steps are followed in developing a test plan? What is top-down testing? What is bottom -up testing? What are guidelines for developing test plans? What do you mean by continuous testing? What are the Myers debugging principles? What is debugging? What is error based testing? Give an example. What is scenario -based testing? What are two types of path testing? Differentiate beta testing and alpha testing? What are the steps involved in successful testing? Define Unit Testing?
Object oriented system development by Ali Brahami Object oriented methodology by Booch A text book on UML by Srimathi