Waterfall Model

SOFTWARE ENGINEERING NOTES PART 1 WATERFALL MODEL The waterfall model is a well-known and well-known version of the SDLC (System Development Life Cycle) for software engineering. The waterfall model is a linear and sequential model, which means that a development phase cannot begin until the previous phase is completed. We cannot overlap phases in waterfall model. “We can imagine the waterfall in the following way:Once the water starts flowing over the edge of the cliff and starts falling towards the bottom of the mountain and this water cannot go back to the top. Similarly waterfall model also works, once a phase of development is completed then we move to the next phase but cannot go back to the previous phase. In the waterfall model, the output of one phase serves as the input for the other phase. The waterfall model consists of the following 5 phases 1: - Requirement phase: - The requirement phase is the first phase of the waterfall model. In this phase the requirements of the system are collected and documented. This phase is very important because the next phases are based on this phase. 2: - Design phase: - The design phase is based on the fact that how the software will be built. The main objective of the design phase is to prepare the blueprint of the software system so that there is no problem in the upcoming phases and the requirements in the requirement phase are resolved. 3:-Implementation phase:- In this phase hardware, software and application programs are installed and database design is implemented. Before the database design is implemented, the software has to go through the testing, coding, and debugging process. This is the longest running phase in the waterfall. 4: - Verification phase: - In this phase the software is verified and it is evaluated that we have made the right product. In this phase, different types of testing are done and every area of the software is checked. Agreed that if we have not verified the software properly and there is a defect in it, then no one will use it, so verification is very important. One advantage of verification is that it reduces the risk of software failure. 5: - Maintenance phase: - This is the last phase of the waterfall. When the system is ready and users start using it, then the problems that come in it have to be solved time-to-time. Taking care of the finished software according to time and maintaining it is called maintenance. There are three types of maintenance in SDLC:1. Corrective maintenance 2. Adaptive maintenance 3. Perfective maintenance. SPIRAL MODEL Spiral model was proposed by BOHEM in 1985. Due to the spiral shape of this model, it is called spiral model. The Spiral model includes both the Waterfall model and the Prototype model, that is, it is a combination of both the Waterfall model and the Prototype model. Spiral model is used for big projects, it is not used in small projects and this model is very expensive. The spiral model consists of the following 4 phases: 1:-Planning 2:- Risk analysis 3:-Engineering 4:-Evaluation 1: - Planning: - In the planning phase all our requirements are collected. In the planning phase, we discuss what we want the software to achieve or what are its goals. 2:-Risk analysis:- In this phase all the risks we face are identified and if any risk is found then its solution is found. 3: - Engineering: - In this phase coding and testing is done and the whole process of software development comes in this phase. 4:-Evaluation:-Whatever software has been prepared in this phase, the customer evaluates it and gives its feedback. SOFTWARE ENGINEERING AND ITS CHARACTERSTICS What is software engineering? Software engineering refers to an engineering in which software is manufactured for computer systems and any other electronic device. In other words, "software engineering is a process in which user needs are analyzed and software is created based on these needs." Software engineers create these software and applications by programming and designing. Software engineering is made up of two words. First software and second engineering. Software is a collection of programs. Software is developed using many programming languages. Engineering means developing products using scientific principles and methods. Why is software engineering needed? This is needed because of the following reasons:To manage large software. for greater scalability. To manage the cost. To manage the dynamic nature of the software. For better quality management. Need of software engineering Large Software In real life, it is easier to build a wall than to build a whole house. Similarly, whenever the size of the software becomes large, then software engineering helps in developing the software. Scalability If we build software on the basis of scientific and engineering concepts then it is easy to create new software. Cost – By following the process of software engineering, we can reduce the cost of software. For this we have to follow the right process. Dynamic nature – The nature (nature) of software always changes and it needs to be changed according to time. Software engineering plays a very important role in this. Quality management – If the method of making the software is better then the quality of the software is also better. Software engineering provides better methods. Advantage of Software Engineering Its benefits are as follows:It reduces the complexity of large software. Big software is always complicated and challenging. The complexity of a large project can be reduced by software engineering because it breaks big problems into smaller problems. Due to which small problems can be solved easily. It reduces the cost (price) of the software. It reduces the time taken to develop the software. By this it is easy to handle big projects. Big projects cannot be completed in a few days. It takes a lot of time and a lot of planning has to be done for this. If we follow the methods of software engineering then big projects can be handled easily. This makes the software reliable. That means the software will be secure and bugs will not come in it. Software becomes more effective with the help of software engineering. Software Features A good software has the following properties:1: - Robustness - The software should have robustness so that defects and failures can be detected in the software. 2: - Security - The security in the software should be better so that the software remains completely secure and it is safe from threats. 3: - Reliability - The software should be reliable, that is, there should not be any defects in it. 4: - Flexibility - The software should be flexible, that is, if some changes are to be made in the software, then it can be done easily. 5: - Testability - Testing of software can be done easily. 6: - Platform independent - Software should be platform independent, that is, it can run in any system. What is Black Box Testing and White Box Testing? What is black box testing? Black box testing is a technique of software testing in which the functionality of the software is tested and the tester does not have knowledge of the internal structure of the software. In other words, "Black box testing is that testing in which the tester does not need to have knowledge of the internal structure of the software and it is not necessary for the tester to have knowledge of coding." Black box testing is also called input-output testing. This testing is called black box testing because the software which is there is like a black box for the tester inside which he cannot see. In this testing only the input and output of the software is taken care of. That's why it is also called Behavioral Testing. In this testing, the tester selects a function and gives it an input to check its functionality. If the function provides correct output then it is passed in testing otherwise it is failed. After this the test team tells the development team about this result and tests the next function. When all the functions are tested and there is a problem in them, then it is sent to the development team to correct it. Advantages of Black Box Testing In this, it is not necessary for the tester to have knowledge of programming language. Black box testing is always tested from the user's point of view, so the problem is easily detected in it. In this, it is not necessary for the tester to know the internal working of the software. In this, test cases can be designed immediately after the completion of the specifications. In this, tester and designer remain independent from each other, so testing remains unbiased in this. This is a very efficient technique for large softwares. Disadvantages of Black Box Testing – It is very difficult to design test cases if the specifications are not clear and concise. In this all the inputs are not tested because the tester does not have time to test all the inputs. If the test has already been completed by the designer, then there is a possibility that the test may be repeated again. It cannot be used to test complex (complex) code. How to do Black box testing? Following are the steps to perform it:In this, the specifications and requirements are first examined. In the second step, the tester creates a positive test scenerio . In this, it selects both valid and invalid input values and checks whether the software is processing them correctly or not. In the third step, the tester develops many test cases such as – decision table, all pairs test, error estimation, cause-effect graph etc. In the fourth step, all the test cases are executed. In the fifth step, the tester compares the expected output with the actual output. In the last step, if any defect is found in the software, then it is fixed and the software is tested again. Black Box Testing Techniques Following are the black box testing techniques:equivalence partitioning Boundary value analysis Cause Effect Graphing Decision Table Technique Requirement Based Testing Error guessing Equivalence partitioning It is a software testing technique in which the input values are divided into valid and invalid parts. In this, all the inputs are not tested one by one, rather the inputs are tested in a group. The advantage of equivalence partitioning technique is that it takes less time to test the software. This technique can be used at all levels of testing like – unit, security testing, alpha beta testing etc. Equivalence partitioning is also called equivalence class partitioning. Boundary Value Analysis Boundary Value Analysis is a black box testing technique which is used to test the boundary value and it is used to find errors in the boundaries of the input data. Boundary is of two types, one lower boundary (where the boundary starts) and the other upper boundary (where the boundary ends) and each boundary has a valid value and an invalid value. Test cases are designed on the basis of both these valid and invalid values and we usually choose one test case from each boundary. Cause effect graphing It is a software testing technique in which the relationship between cause and effect is developed. Its steps are as follows:In this, inputs (cause) and outputs (effect) are identified. In this cause effect graph is developed The graph is converted into a decision table. Finally the decision table rules are converted into test cases. Decision Table Technique Decision Table Technique is a systematic approach in which many input combinations and their system behavior are stored in the form of a table. This technique is suitable for functions that have a logical relationship between two or more inputs. Requirement based testing Requirement based testing is a software testing technique that validates the requirements given in the SRS of the software system. Error Guessing Error guessing is a technique in which no particular method is used. It completely depends on the experience of the tester. In this, the tester guesses the problem of the software based on his experience. Levels of Black box testing Following are the levels of black box testing:Integration Testing System Testing Acceptance Testing Integration Testing – Integration testing is a method of software testing in which two or more software units or modules are combined together and tested in a group. System Testing System Testing is a type of testing technique in which the entire system is tested. In system testing, the behavior (nature) of the entire software product is checked on the basis of software requirement specification (SRS). Acceptance Testing – Acceptance Testing is a testing technique in which it is determined whether the software meets the requirements specified by the user or not. Types of Black Box Testing There are three types of black box testing:Functional testing Non-functional testing R egression testing Functional testing Functional testing is a type of black box testing which is used to verify the functional requirements of the software. The main purpose of this testing is to test each function. Non-functional testing – It is a type of software testing which is used to test the non-functional parameters of the software like – reliability, load test, and performance etc. The main purpose of this testing is to test the reading speed of the software system. Regression Testing – Regression testing ensures that whether the change made in the software is causing any problem in the working of the software or not. That is, it checks that if we make some changes in the software, then there is any bad effect in the working of the software or not. White Box Testing The testing in which the tester has knowledge of the internal structure of the software is called white box testing. This type of testing is based on the working inside the software. This testing is called white box because the software which is there is like a white box for the tester inside which he can see. In other words, "White box testing is a software testing technique in which the internal structure, design and coding of the software is tested." In this type of testing, the tester has knowledge of programming. The major advantage of this testing is that we can detect errors at the beginning stage of software development. The main purpose of this testing is to verify the input output flow and to improve design, usability, and security. In this, the code is visible to the tester, hence it is also called clear box testing, transparent box testing and glass box testing. In this testing, the developer tests each line of code of the program. White box testing is performed by the developers and then the software is sent to the testing team for black box testing. Advantages of White Box Testing Its benefits are as follows:- It optimizes the code so hidden errors are found by it. Test cases of white box testing can be easily automated. This testing can be started immediately in SDLC even when GUI is not available. In this all the code and structure are tested. Disadvantages of white box testing Its disadvantages are as follows:Its main disadvantage is that it is very expensive. To do this testing, the tester should have knowledge of programming language. In this, to rewrite the code, test cases also have to be rewritten. It is very complex. It takes a lot of time to perform it. Types of White Box Testing Techniques Following are the White box testing techniques:Data flow testing control flow testing branch testing statement testing Decision testing Data Flow Testing – It is a group of testing strategies that examines the control flow of the program. Control flow testing This testing technique determines the execution order of the statements of the program through the control structure. The control structure of a program is used to develop the test cases of the program. Branch Testing – Branch testing is used to cover all the branches of the control flow graph. Statement testing – This testing is done to design the white box test cases. In this technique, all the statements of the source code are definitely tested at least once. Decision Testing In this testing, while, do while, for loop and if statement etc. are used to test the statements. In this, true or false results are reported. How to do White box testing? The steps to perform it are given below:First of all all test scenarios and test cases are designed and they are given priority. In this step, the code is studied at runtime to check the resource utilization. Testing of the internal subroutine is done in this step. In this step control statements are tested such as – loops and conditional statements. Security testing is done in the last step so that possible security flaws can be checked. FEASABILITY STUDY Feasibility Study Testing the capability of the system for the success of any system is called Feasibility Study. The main objective of the feasibility study is to determine whether it is financially and technically possible to develop the system. The purpose of feasibility study is not to solve the problem but to determine whether the problem can be solved or not. In this, all the problems coming in the system are analyzed, in this the information of the system is deeply examined and it is determined that how success can be achieved in developing the system. Types of feasibility studies Feasibility study is of the following three types:1:-Technical Feasibility 2:-Operational Feasibility 3:-Economic Feasibility 1: - Technical Feasibility: - In this feasibility, the technical requirements of the system are determined. In this, it is seen that the technology required for the proposed system is available and how that technology should be integrated into the system. Technically competent experts are also required to handle all kinds of complexities coming in the new technology. 2: - Operational Feasibility: - In this feasibility, it is determined that how a proposed system will solve the problems and what kind of changes have come in the system? In this, it is seen whether the system is beneficial for the users or not and whether it is able to meet the needs or not. 3: - Economic Feasibility: - In this feasibility, it is determined that how much will be spent in the proposed system and how much benefit will be available in it? Economic feasibility is also called cost benefit analysis.