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Sqa unit1

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Sqa unit1

  1. 1. UNIT-I CS E71 SQA & TESTING Page 1 INTRODUCTION-SOFTWARE TESTING Software testing is a process, or a series of processes, designed to make sure computer code does what it was designed to do and that it does not do anything unintended. Software should be predictable and consistent, offering no surprises to users. OVERVIEW Software testing is a technical task, but it also involves some important considerations of economics and human psychology. In an ideal world, we would want to test every possible permutation of a program. In most cases, however, this simply is not possible. Even a seemingly simple program can have hundreds or thousands of possible input and output combinations. Creating test cases for all of these possibilities is impractical. Complete testing of a complex application would take too long and require too many human resources to be economically feasible. SCOPE OF SOFTWARE TESTING The function of software testing is to detect bugs in order to correct and uncover it. Software Testing is classified into two types of software testing: Manual Scripted Testing and Automated Testing The software testing have different goals and objectives which include: 1. Finding defects. 2. Gaining confidence in and providing information about the level of quality. 3. Preventing defects. Objectives of testing  Executing a program with the intent of finding an error.  To check if the system meets the requirements and be executed successfully in the Intended environment.  To check if the system is “ Fit for purpose”.  To check if the system does what it is expected to do. Objective of a Software Tester  Find bugs as early as possible and make sure they get fixed.  To understand the application well.  Study the functionality in detail to find where the bugs are likely to occur.
  2. 2. UNIT-I CS E71 SQA & TESTING Page 2  Study the code to ensure that each and every line of code is tested.  Create test cases in such a way that testing is done to uncover the hidden bugs and also ensure that the software is usable and reliable SOFTWARE DEVELOPMENT LIFE CYCLE PROCESS Software Development Life Cycle (SDLC) is a procedural process in the development of a software product. The Process is carried out in steps to explain the whole idea about how to go through each product. The classification of SDLC is follows: 1. Planning 2. Analysis 3. Design 4. Software Development 5. Implementation 6. Software Testing 7. Deployment 8. Maintenance
  3. 3. UNIT-I CS E71 SQA & TESTING Page 3  PLAN (P): Device a plan. Define your objective and determine the strategy and supporting methods required to achieve that objective.  DO (D): Execute the plan. Create the conditions and perform the necessary training to execute the plan.  CHECK (C): Check the results. Check to determine whether work is progressing according to the plan and whether the results are obtained.  ACTION (A): Take the necessary and appropriate action if checkup reveals that the work is not being performed according to plan or not as anticipated. PHASES of SDLC  Requirement Specification and Analysis  Design  Coding  Testing  Implementation  Maintenance Requirement Specification and Analysis User Requirement Specification (USR) Software Requirement Specification (SRS)
  4. 4. UNIT-I CS E71 SQA & TESTING Page 4 Design The output of SRS is the input of design phase. Two types of design High Level Design (HLD) Low Level Design (LLD) The Design process Breaking down the product into independent modules to arrive at micro levels. Two different approaches followed in designing  Top Down Approach  Bottom Up Approach
  5. 5. UNIT-I CS E71 SQA & TESTING Page 5 Coding Developers use the LLD document and write the code in the programming language specified. Testing The testing process involves development of a test plan, executing the plan and documenting the test results. Implementation Installation of the product in its operational environment. Maintenance After the software is released and the client starts using the software, maintenance phase is started. 3 things happen - Bug fixing, Upgrade, Enhancement Bug fixing – bugs arrived due to some untested scenarios. Upgrade – Upgrading the application to the newer versions of the software. Enhancement - Adding some new features into the existing software.
  6. 6. UNIT-I CS E71 SQA & TESTING Page 6 SOFTWARE LIFE CYCLE MODELS WATERFALL MODEL V-PROCESS MODEL SPIRAL MODELS PROTOTYPE MODEL INCREMENTAL MODEL EVOLUTIONARY DEVELOPMENT MODEL SOFTWARE TESTING TYPES Manual testing This type includes the testing of the Software manually i.e. without using any automated tool or any script. In this type the tester takes over the role of an end user and test the Software to identify any un-expected behavior or bug. There are different stages for manual testing like unit testing, Integration testing, System testing and User Acceptance testing. Testers use test plan, test cases or test scenarios to test the Software to ensure the completeness of testing. Manual testing also includes exploratory testing as testers explore the software to identify errors in it. Automation testing Automation testing which is also known as Test Automation, is when the tester writes scripts and uses another software to test the software. This process involves automation of a manual process. Automation Testing is used to re-run the test scenarios that were performed manually, quickly and repeatedly.ss
  7. 7. UNIT-I CS E71 SQA & TESTING Page 7 Apart from regression testing, Automation testing is also used to test the application from load, performance and stress point of view. It increases the test coverage; improve accuracy, saves time and money in comparison to manual testing. THE PSYCHOLOGY OF TESTING One of the primary causes of poor program testing is the fact that most programmers begin with a false definition of the term. They might say: “Testing is the process of demonstrating that errors are not present.” “The purpose of testing is to show that a program performs its intended functions correctly.” “Testing is the process of establishing confidence that a program does what it is supposed to do.” These definitions are upside-down. THE ECONOMICS OF TESTING Given this definition of program testing, an appropriate next step is the determination of whether it is possible to test a program to find all of its errors. We will show you that the answer is negative, even for trivial programs. In general, it is impractical, often impossible, to find all the errors in a program. This fundamental problem will, in turn, have implications for the economics of testing, assumptions that the tester will have to make about the program, and the manner in which test cases are designed. To combat the challenges associated with testing economics, you should establish some strategies before beginning. Two of the most prevalent strategies include black-box testing and white-box testing techniques. VERIFICATION AND VALIDATION Software testing is one element of a broader topic that is often referred to as verification and validation (V&V). Verification refers to the set of activities that ensure that software correctly implements a specific function. Validation refers to a different set of activities that ensure that the software that has been built is traceable to customer requirements. Boehm states this another way: Verification: "Are we building the product right?" Validation: "Are we building the right product?" The definition of V&V encompasses many of the activities that we have referred to as software quality assurance (SQA). Verification and validation encompasses a wide array of SQA activities that include formal technical reviews, quality and configuration audits, performance monitoring, simulation, feasibility study, documentation review, database review, algorithm analysis, development testing, qualification testing, and installation testing.
  8. 8. UNIT-I CS E71 SQA & TESTING Page 8 Quality is incorporated into software throughout the process of software engineering. Proper application of methods and tools, effective formal technical reviews, and solid management and measurement all lead to quality that is confirmed during testing. Miller relates software testing to quality assurance by stating that "the underlying motivation of program testing is to affirm software quality with methods that can be economically and effectively applied to both large-scale and small-scale systems. LEVELS OF SOFTWARE TESTING Software Testing is carried out at different levels throughout the entire software development life cycle. Each and every component should be tested functionally and structurally. Testing is essential during the integration of software components to ensure that each combination of component is satisfactory. System and acceptance testing are then followed. The IEEE standard on software verification and validation identifies four levels of testing. TYPES OF SOFTWARE TESTING Unit test: In this phase, each unit is separately tested, and changes are done to remove the defects found. Since each unit is relatively small and can be tested independently, they can be exercised much more thoroughly than a large program. Customer Requirements Acceptance Testing Requirements System Testing High level design Integration Testing Detalied Design Component Testing
  9. 9. UNIT-I CS E71 SQA & TESTING Page 9 Integration testing: During integration, the units are gradually assembled and partially assembled subsystems are tested. Testing subsystems allows the interface among modules to be tested. By incrementally adding units to a subsystem, the unit responsible for a failure can be identified more easily. System testing: The system as a whole is exercised during system testing. Debugging is continued until some exit criterion is satisfied. The objective of this phase is to find defects as fast as possible. In general the input mix may not represent what would be encountered during actual operation. Acceptance testing: The purpose of this test phase is to assess the system reliability and performance in the operational environment. This requires collecting (or estimating) information about how the actual users would use the system. This is also called alpha-testing. This is often followed by beta-testing, which involves actual use by the users. Regression testing: When significant additions or modifications are made to an existing version,regression testing is done on the new or "build" version to ensure that it still works and has not "regressed" to lower reliability. Unit Testing This type of testing is performed by the developers before the setup is handed over to the testing team to formally execute the test cases. Unit testing is performed by the respective developers on the individual units of source code assigned areas. The developers use test data that is separate from the test data of the quality assurance team. The goal of unit testing is to isolate each part of the program and show that individual parts are correct in terms of requirements and functionality. Limitations of Unit Testing Testing cannot catch each and every bug in an application. It is impossible to evaluate every execution path in every software application. The same is the case with unit testing. There is a limit to the number of scenarios and test data that the developer can use to verify the source code. So after he has exhausted all options there is no choice but to stop unit testing and merge the code segment with other units.
  10. 10. UNIT-I CS E71 SQA & TESTING Page 10 System Testing This is the next level in the testing and tests the system as a whole. Once all the components are integrated, the application as a whole is tested rigorously to see that it meets Quality Standards. This type of testing is performed by a specialized testing team. System testing is so important because of the following reasons: System Testing is the first step in the Software Development Life Cycle, where the application is tested as a whole. The application is tested thoroughly to verify that it meets the functional and technical specifications. The application is tested in an environment which is very close to the production environment where the application will be deployed. System Testing enables us to test, verify and validate both the business requirements as well as the Applications Architecture. Integration Testing The testing of combined parts of an application to determine if they function correctly together is Integration testing. There are two methods of doing Integration Testing Bottom-up Integration testing and Top Down Integration testing. S.N. Integration Testing Method 1 Bottom-up integration This testing begins with unit testing, followed by tests of progressively higher-level combinations of units called modules or builds. 2 Top-Down integration This testing, the highest-level modules are tested first and progressively lower-level modules are tested after that. In a comprehensive software development environment, bottom-up testing is usually done first, followed by top-down testing. The process concludes with multiple tests of the complete application, preferably in scenarios designed to mimic those it will encounter in customers' computers, systems and network. TYPES OF SOFTWARE TESTING There are different methods which can be use for Software testing. This chapter briefly describes those methods. Black Box Testing
  11. 11. UNIT-I CS E71 SQA & TESTING Page 11 The technique of testing without having any knowledge of the interior workings of the application is Black Box testing. The tester is oblivious to the system architecture and does not have access to the source code. Typically, when performing a black box test, a tester will interact with the system's user interface by providing inputs and examining outputs without knowing how and where the inputs are worked upon. Advantages Disadvantages Well suited and efficient for large code segments. Code Access not required. Clearly separates user's perspective from the developer's perspective through visibly defined roles. Large numbers of moderately skilled testers can test the application with no knowledge of implementation, programming language or operating systems. Limited Coverage since only a selected number of test scenarios are actually performed. Inefficient testing, due to the fact that the tester only has limited knowledge about an application. Blind Coverage, since the tester cannot target specific code segments or error prone areas. The test cases are difficult to design. White Box Testing White box testing is the detailed investigation of internal logic and structure of the code. White box testing is also called glass testing or open box testing. In order to perform white box testing on an application, the tester needs to possess knowledge of the internal working of the code. The tester needs to have a look inside the source code and find out which unit/chunk of the code is behaving inappropriately. Advantages Disadvantages As the tester has knowledge of the source code, it becomes very easy to find out which type of data can help in testing the application effectively. It helps in optimizing the code. Extra lines of code can be removed which can bring in hidden defects. Due to the tester's knowledge about the code, maximum coverage is attained during test scenario writing. Due to the fact that a skilled tester is needed to perform white box testing, the costs are increased. Sometimes it is impossible to look into every nook and corner to find out hidden errors that may create problems as many paths will go untested. It is difficult to maintain white box testing as the use of specialized tools like code analyzers and debugging tools are required. Grey Box Testing
  12. 12. UNIT-I CS E71 SQA & TESTING Page 12 Grey Box testing is a technique to test the application with limited knowledge of the internal workings of an application. In software testing, the term the more you know the better carries a lot of weight when testing an application.Mastering the domain of a system always gives the tester an edge over someone with limited domain knowledge. Unlike black box testing, where the tester only tests the application's user interface, in grey box testing, the tester has access to design documents and the database. Having this knowledge, the tester is able to better prepare test data and test scenarios when making the test plan. Advantages Disadvantages Offers combined benefits of black box and white box testing wherever possible. Grey box testers don't rely on the source code; instead they rely on interface definition and functional specifications. Based on the limited information available, a grey box tester can design excellent test scenarios especially around communication protocols and data type handling. The test is done from the point of view of the user and not the designer. Since the access to source code is not available, the ability to go over the code and test coverage is limited. The tests can be redundant if the software designer has already run a test case. Testing every possible input stream is unrealistic because it would take an unreasonable amount of time; therefore, many program paths will go untested. Black Box Vs Grey Box Vs White Box Testing S.N. Black Box Testing Grey Box Testing White Box Testing 1 The Internal Workings of an application are not required to be known Somewhat knowledge of the internal workings are known Tester has full knowledge of the Internal workings of the application 2 Also known as closed box testing, data driven testing and functional testing Another term for grey box testing is translucent testing as the tester has limited knowledge of the insides of the application Also known as clear box testing, structural testing or code based testing 3 Performed by end users and also by testers and developers Performed by end users and also by testers and developers Normally done by testers and developers 4 Testing is based on external expectations - Internal behavior of the application is unknown Testing is done on the basis of high level database diagrams and data flow diagrams Internal workings are fully known and the tester can design test data accordingly 5 This is the least time consuming and exhaustive Partly time consuming and exhaustive The most exhaustive and time consuming type of testing
  13. 13. UNIT-I CS E71 SQA & TESTING Page 13 6 Not suited to algorithm testing Not suited to algorithm testing Suited for algorithm testing 7 This can only be done by trial and error method Data domains and Internal boundaries can be tested, if known Data domains and Internal boundaries can be better tested WEYUKER'S ADEQUACY AXIOMS An established principle; a self-evident truth (Concise Oxford). Choice of this term may have been unfortunate. (1) If the adequate test set is infinite (or even very large) it would be impossible to satisfy the criterion. Weyuker does not explore the definition of “very large” any further. (2) Exhaustive testing (testing every point in the domain) can be assumed to be adequate. An important part of testing is identifying a subset of the test domain which represents the whole domain. 3) The addition of more test cases to an already adequate set does not make it inadequate. Therefore, the subset of the domain does not have to be the smallest possible subset. In some instances a larger subset might be easier to identify. (4) A program cannot be assumed to be adequate if it has not been tested at all. Dynamic testing assumes that the program has at least one input. (5) These axioms support program-based testing, not functionality or specification-based testing. Therefore, two programs which perform the same function but are implemented differently would require different test sets. (6) Programs with the same shape (structure) may require different data sets to traverse their structure. The program P taken as a whole may not be able to stimulate all possible actions of component Q. Q must be tested in its own right. Example: component Q could be a sorting routine. What if program P always provides data already sorted? Testing must take into account the added complexity and interaction which occurs when two programs are composed. Hence the traditional need for integration testing.

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