Model Driven Development Vs Test Driven Development Computer Science Essay

pattern determined Development Vs sampleing drive Development Computer perception Essay set drive suppuration is a top-down, traditional burn up that has been around for a long time. Test Driven Development (TDD) is a bottom-up, new move up in the sense that it has picked up its value in the recent classs. The focus of MDD as the name implies is on the modelings instead than on inscribe that guides the victimization of softw atomic number 18 whereas focus of TDD is on the tests. There hurl been several changes to MDD since the beginning to deal with the changing environment and complexities raised by projects. TDD started as a part of extreme scheduleming (XP) methodology and has gained popularity among legion(predicate) conk proscribeders as a separate practice itself. Traditional, hard cored MDD developers be wedded to developing bundle that seems more natural to them considering it to be an conducting attack. TDD developers prelude the fuss in a tot alon ey several(predicate) prospect concentrating on customer views of the governing body. There are advantages and disadvantages to both approaches. For a high t match little of voice software crop that meets the goals of the organization, it is important to control and apply the roughly competent methodology tour making original(p) trade-offs if obligatory. The best approach to keep an eye on dep remainders on several factors including the type of organization, type of project, and experience the developers restrain. This paper is aimed at explaining influence operate and Test Driven culture along with trip study and observations. 1. Model Driven Development or MDD.Model evict be precisely defined as a description of a system from a particular perspective, omitting irrelevant detail so that the characteristics of engage are seen more clearly. (Source Patterns Model-Driven Development exploitation IBM Rational computer software Architect) Consider an illustration in which thither is a pressing wrinkle use up more(prenominal) as automation of certain lickes and determineing the selective information collected in the stage business. In this office staff a credit line exists and there are population who are performing certain business activities in certain way. These are the people who are thinking of having a mother fucker or a software crossingion to help them increase their harvest-feastivity and their functionality. These people who are c altogethered Domain Experts or Subject Matter experts or Business Experts whop what they want. However, they currently do non have roughly(prenominal) software product that departing help them to meet their needfully. In this situation Domain Experts are the driving force. They do things in a certain way and expect the software product essential for them meet their take should in addition do things in that manner. However, they do non know how a new software product allow look l ike and how it result help them to meet their needs. People who develop this software product understand the needs, exactly they may miss the intricacies of the desired end product. construction a MODEL provide help alleviate this situation. A MODEL provide be a diagram, an animation or a presentation. If the bundle that has to be essential is really itty-bitty or involves 1 or 2 people, then the procedure need not be so over very much structured, even though it helps. However, slice developing a boastfully product which allow for involve tens or hundreds of people having different expertise, model will help them to accomplish this easily. A new product development bring in a Model is absolutely incumbent. This is analogous to a civil Engineer creating a model of Building in the lead it is actually construct.Model Driven Development (MDD) is a methodology that focuses on intention models at an twinge level without considering the implementation details that guide the development process, foc apply on one part of the system to manage complexity. Models help to analyze the problem and visualize the process. Most comm barely used language for this bearing is merge Modeling Language (UML). It establishes certain vocabulary and structure so as to understand and communicate between various developers. Artifacts are defecated from the models, so the models are machine-read qualified, which is an important aspect of MDD.MDD is alike called as Model Driven engineering science. An implementation of MDD is given by Object Management Group (OMG)s Model Driven Architecture (MDA). Focus of MDA is on forward engineering, i.e. creating computer enter from molding diagrams. Apart from MDA, there are also other views of MDD much(prenominal)(prenominal) as Domain Oriented Programming, Agile Model Driven Development, etcetera MDA uses curriculum-independent model (PIM) to describe the system functionality as the first step. Platform Independent Mo del (PIM) is a generic way of representing the end view of the product without considering both technology or platforms going to be used. This model righteous transforms the Business requirements into a Model. This format does not contain each particular software code but shows the end state of the product in one of the Model development modes such as Diagrams, Flow Charts, and Animations etc. found on the PIM and considering some economic conditions or availability, a decorous platform is selected to develop the software. A model is then converted from PIM to platform special model or PSM. . This contains software code at a high level. Platform is a loose word in this context. This push aside be referred to type of hardware, software, operating system, programming language or combination of any of these put together. That is why choosing a platform is related to economic viability also.PSM outhouse be archetype of Developers model where as PIM give the gate be thought of Domain Experts or contain drug exploiters model.UML representation victimisation IBMs Rational roseate heap be considered as PIM. Whereas, tools like IBM WebSphere Studio and Borland Together/J are used for developing PSM. In these, we have CODE mess and MODEL VIEW. These two views are synchronized together. When code is changed in jurisprudence View, it is reflected in the Model View and vice versa. The models may contain rooted(p) and variable data, business requirements, presentation elements (forms, reports). If one of these elements changes, they can be unified into the model to see the changes that occur due to interdependencies. Based on the contacts, all the other depending code can be changed accordingly to accommodate these changes.Models also describe what is called the Gap Analysis. Models are first built with an Ideal situation, but in reality the business processes and other aspects may be different. Therefore, the models will show the difference between the Real Life situation and the End State Ideal situations. This will help the Business units to define the changes in Business Practices or the Developers to meet the Business needs and bridge the gap. A well defined Structured System Analysis and Design (SSAD) is ask to develop software based on Models. In this process, the design (Model) is interpreted as the basis to start with the development and as the development process is declared, it is analyzed with the design and tested against the Model and re-visited to meet the requirements. Hence, software development using MDD approach requires Domain (Business) experts, software developers, Team leaders and integrating experts. Someone should also be able to play a data link role to understand both sides of the table Business side and software program side. This person will help each of the expert groups to understand the needs of other groups and will bridge the gap. Number of iterations in the project development process will be reduced drastically if this Liaison person has unassailable knowledge and is an expert on both sides.MDD is used with some development processes such as waterfall model, iterative model, spiral model, etc. In MDD approach, a model plays an important role and forms the basis or driving mechanism to develop a software product. Test Driven DevelopmentTest Driven Development (TDD) started its roots in primitive Programming (XP) approach. Later on, it became a popular method by itself. TDD was originally called Test maiden Programming. TDD can best be expound in triad words as Red-Green-Refactor (source Kent Beck). Simple nerve center of TDD is to keep tests before the code is written. setoff, unit tests are written from the requirements. These tests will in spades fail because the code for it has not been written. In order to spell the tests, it is necessary for the developer to understand the requirements well. Then, code that implements the test casings is written. The code that is written should be just enough so that the tests outmatch, no more, no less. This means that no expectancy some the future story must be make. Test driven approach is then there approach. This means that code is written at that time from the drug user story requirements without making any assumptions or predictions around future. After composing the code, the tests are run and seen if they succeed. If they do, then programmer can be as veritabled that the requirements were met. After this, a process called refactoring is done. This refers to improving the caliber of code and removing any duplication in the code. If the design is changed for the better, the developer can be sure he is not breaking any functionality by rail the tests again. This process is repeated for the test cases that follow. This process is shown as a flow chart belowSource http//en.wikipedia.org/wiki/Test-driven_developmentThere are different issues to consider in this process. Test ca ses are written taking small steps at a time, such as implementation of one method. It is important to know the size of the test case and when the test case exceeds its limit of functionality to test. A test case contains the sideline condition that specifies the systems state, an event that is to be tested, and eventually systems state after the event has occurred. Al to the highest degree every language has associated tools for writing these tests. In general, they are XUnit tests available for each language. For example, java has JUnit, C++ has cppUnit, .Net has NUnit, etc. The come in of designing that has to be done in TDD depends on developer. In Extreme Programming, no designing is done, directly jumping to test cases. However, some developers prefer to spend some time on design. Too much time should not be spent on the designs and deciding on that right amount of time to spend on it comes with experience. As suggested by Dave Chaplin, it takes al about a year for a near developer to learn most of the techniques in TDD. He divides the learning process in three symbolises. First stage would take three months to master writing the tests correctly. TDD is a on the whole different approach to take in developing software and most developers recollect that hardest part about it is getting used to it and thinking in that direction. It takes another six months to learn about Mock inclinations. Last would be to be able to draw UML diagrams in a TDD perspective. This takes about three months. Those that become familiar with TDD welcome many an(prenominal) advantages in it. These advantages are explained after in the paper. Pair programming is considered one of the best ways to develop a program using TDD. This is because another person can buy in sure you are going in right path. It is hard to function developers believe that this approach works. Also, management believes that it is a waste of money to make two people work on one feature while they c an work on different features.Through test driven development, the focus is on customers requirements. TDD is now part of many other methodologies, such as Scrum, Agile Unified carry through (AUP), and Rational Unified Process (AUP). TDD gives confidence to the developer and produces enthusiasm as they can see parts of the program coming together when they run the tests and see them pass. Case StudyResults of TDD and MDD are seen more efficacious by example. Therefore, I consider a case in which a Software Engineering class was given a choice of either doing MDD or TDD project. The projects were done for the aforesaid(prenominal) problem using different approaches. It was a calendar program that consisted of certain functionalities to fulfill. For TDD people, six user stories were given one after another without knowing what the next user story is. MDD people were given a problem definition and they were to confront graphical user interface, design, code, tests at regular interv als. The functionalities that had to be implemented included finding the undermentioned next date, previous date, zodiac sign, day of the week, next Friday the 13th, number of shopping old age left until Christmas. These were each given as a user stories to TDD people. From the results of these, the followers statistics were makeModel Driven Development approach resultsCriteriaMDD substance abuser 1substance abuser 2substance abuser 3User 4User 5User 6Time To Code (hrs)852898.671117Time to Test (hrs)2151333.32NCSS (non comment source statements) 275600692499280Number of Test Cases 10914251Technology UsedVBA chocolate java (using Eclipse)C.NET VS2008C VS ExpressCDecision Complexity 7959referential Complexity2652Cyclomatic Complexity10511183GUIyesyesyesyesyesyesTest Driven Development approach resultsCriteriaTDDUser 7User 8User 9User 10User 11User 12User 13User 14User 15User 16User 17User 18Time to code16.52217332813.53319.533152812.75NCSS(non comment source Statements)34939727665 42402331095279196298328277Test casescl84124701072471128826256889128TechnologyC.NET VS2008 burnt umber JavaJavaVB.Net ExpressCVB .NetVBAJavaJavaVB.NETJavaDecisional Complexity1066676769711562577714581Referential Complexity12434024243419102916029Cyclomatic Complexity118109117100651211498115986115110GUInonononoyesnononononoNonoNumber of Times Refactorednone12none5none546113ObservationsEven though there were almost twice as many people who did TDD as MDD, certain trends can be seen from the statistics. Since majority of the projects were developed using object oriented technology such as Java and C, most of the observations are made based on these languages only. First and major difference that can be seen is creation of GUI. Only 1 out of 12 TDD people developed GUI while all of the six people who did through MDD developed it. One of the fences for this is that in MDD, designing of GUI was first part of the task. In TDD, although there are tools that test a user interface, it is hard to obtain them and so user has to manually test them. Since it wasnt part of the requirement also, many had chosen to omit it.I noticed that neatest and well designed code came from most of MDD people. Even though there is refactoring in TDD, many had chosen not to do it. This can be seen by the statistics that 6 out of 12 people have either not done refactoring at all or did it only once. As research suggests, TDD is supposed to lead to high reference code. However, most of TDD projects code was of less quality. This comes to the point that in order to successfully carry out TDD, experience is needed. The lack of experience that most people had in doing a TDD might have been a factor for such quality. many of TDD people had no experience in TDD methodology including me. As suggested by Dave Chaplin, in order to carry out TDD effectively, minimum one year of learning the techniques involved in the approach is needed for a serious developer. Even though the quality and design is n eater in MDD, number of lines of code was much less in TDD than MDD projects. In object oriented languages such as Java and C, MDD projects had lines of code as 518 on an ordinary while TDD projects had 350. This is partly due to refactoring eliminating unnecessary conditions and mostly due to the reason that since code was developed based on test cases, just about enough code that was necessary was written. Since the whole point of TDD is to start out with test cases, TDD projects have more test cases compared to MDD projects. For object oriented languages, TDD tests were 124 on average while MDD was 100. Although theory says that TDD results in highly cohesive and broadly coupled, but in practice, it is seldom like that. This point can be seen in this study. Most of the MDD projects were more cohesive and loosely coupled resulting in more reusable code compared to TDD. In TDD projects, it was seen that most of them had 2 or 3 classes at a maximum reducing cohesive disposition an d reusability. I observed that this is due to unpredictability of future user stories. MDD people can carefully plan the code such that it results in certain functions that can be used by other functions. In object oriented languages, correct amount of responsibilities and collaboration among objects in my opinion can be done more effectively if more designing is done. This is because it is much easier to see visually through the models. The reusability of the code in TDD also depends on the order of the user stories given. Most people reused day of the week code in shopping eld till Christmas user story or Friday the 13th user story. Suppose that the user stories are given in a different order, then different approaches might be taken that might not result in the efficient switch of code. Refactoring tells you to omit duplications and keep the code clean, but the logic of the code will not change. In our case, if suppose number of shopping days left before Christmas was given be fore day of the week user story, then different approach might have been taken and the reusability of the day of the week code wouldnt have existed. It is easier to see collaborations and responsibilities of objects when the whole picture of the problem is present. Even the small amount of reusability that existed in TDD was due to the logical order in which the user stories were given.The time spent on the whole project for TDD is much less than MDD. Considering object oriented languages, TDD average time spent was 21 hours while MDD was 42 hours (almost double). TDD is proven to be faster and easier technique than MDD. In TDD, concentration is on current user story and it is faster to write test cases and code directly from user requirements. The time spent on test cases is paid off since no debugging has to be done at the end.Time and effort can be distributed and planned in advance in MDD. However, in TDD, since the amount of time and effort for the next user stories is hard to predict, it is difficult to plan. Some user stories take less amount of time while others consume lot of time. This can be seen in the case study. Most people said that finding zodiac sign took very less time and effort compared to finding the number of shopping days till Christmas . Pros and Cons of Using MDD approachFrom research and experience, these are some of the observations that were made on the MDD approach in general. A model in projects has following advantages It helps to break down the project into smaller code development pieces or facultys which can be assigned to different teams.It helps each team to understand their role and how their part of the development is mingled into the whole product development The project managers and team leaders will understand on how to integrate all the modules and do examination.The end user will be able to visualize the integrated end product.If enough of time is spent in make a model properly, even though it takes time and effort , it will greatly reduce the time to build the product. A properly built model will also help in reducing the iterations of testing process, thus creating the integrations much quicker.There is also an economic advantage of edifice the models. A model will help to present a product to the investors easily and attract investments to fund the projects.Some disadvantages of using MDD approach The disadvantages of using MDD approach are not related to the approach itself, but rather it is related to the application of this approach. If MDD is not used properly, there will be extended delays in the product developments. Some of these possible setbacks are Building a Model will take lot of time and resources. MDD is not always fit for all approach. The project and product has to be analyzed before this approach is taken.Some people visualize a Model as an abstraction layer hiding all the complications of the product development process. Too much of abstraction may be good to certain aud ience in the project, but it over all defeats the purpose of building a model in the first place. So, care should be taken as not to ABSTRACT too much.If proper resources, such as, proper Domain experts are not involved while building a model, then the model as well as end product will be disastrous failure. MDD should not always be thought of the end point. Always underlying approach for each module should be associated with proper testing. Failure to consider the real life situations also causes the MDD unusable. The key to the whole process of Product development using MDD approach is having a proper liaison between Business group and IT group. Pros and Cons of Using TDD approachSome of the advantages of using TDD areSince test cases are developed first, developer understands the requirements thoroughly in order to write them. The focus is on the functionality perspective of the client. TDD involves taking small steps at a time and snap on one task at a time. Even though it cons umes lot of time to write many unit test cases screen all possibilities, this makes it an advantage as it avoids debugging at later stages in the project. finding bugs as early as possible is always beneficiary in terms of time and cost. Fixing bugs at a later stage is difficult because it is hard to determine what caused the bug. Since just enough code to pass the test is written, TDD will result in thorough testing application all possible paths. If tests are written well, then it will produce stable code.Code is developed faster and there is work piece of code at every level, which inspires confidence and encourages the developer. Developer is aware of the progress made and can set goals to achieve a particular goal.TDD results in good design because of many factors. With experience, TDD can be a very effective method as it lets the developer think in small units of code jumper cable to modularity and good design. This is also the result of looking at the problem from custom ers perspective to understand how it will be implemented. Refactoring also leads to producing good designs. Mocking and faking is good in the sense that it will define the boundaries of the classes. This is because through mocking, you will find out what your classes should and should not know about the other class. This is the basic essence of encapsulation in any object oriented language.The test cases provide punt for faster regression testing. On next iteration or anytime in future, when you add more tests, you can run all the tests to make sure that it works and if it doesnt, it is easy to see what part of the code broke. Some disadvantages with TDD approach areTDD requires commitment and supporting management. Developers should be committed and write proper tests. If the tests are deleted or changed accidentally or purposefully, it will give bogus impression that the code is bugs-free. Support from management is important and they have to believe that this methodology works . If either of them does not exist, then TDD approach fails.Functional tests need to be done for programs that use a database or for creating user interfaces. For such things, using TDD approach is difficult. Tests and code are written by the same person most of the time and if the developer overlooks certain things, then it will affect the code as well and may not result in what is supposed to happen. If he interprets the requirements wrong, then the tests he writes and the code that implements them will let go out to be wrong and will lead to code that will not be as efficient as it should be. Another example would be if the developer doesnt check for certain specific inputs, then the code that needs to implement that will never be implemented.Having large number of working unit tests may build up over confidence that will lead to less concentrations on additional activities such as quality assurance evaluations. Unit tests only tell if the piece of code you wrote works. otherwi se tests such as domain testing, integration testing, etc have to be done. substance of coverage and details of testing that is done in TDD development cannot be reproduced at a later stage. So, these tests become an important aspect and it is necessary that they are well-written.There is no way to predict the type of user stories and it is not possible to gain a complete understanding of the system from the user stories. This leads to extensive code rewriting and refactoring.WHEN to use WHAT?This leads to the question of when is it enamor to use TDD and when is it appropriate to use MDD. Software development is a process of developing a product to meet a certain business need. In a well defined environment and in large houses Software Development is done using the techniques described in Software Engineering and experience gained over the years. Many factors have to be taken into consideration when deciding on the methodology to use. These include things such as type of organizati on, management, type of project, experience of the developers, and availability of effective tools. Type of sendSoftware development is done under two major draw 1. To develop altogether a new product a. A product that never existed before, but there is a need in the minds of people. A great example of this in recent years is Youtube. There was no such product before, however, people had thought about having some potpourri of sharing videos. So, there is direc