Model Driven Development Vs Test Driven Development Computer Science Essay

sit around Driven Development Vs ladder Driven Development Computer perception Essay work driven using is a top-down, traditional entree that has been around for a long cadence. riddle Driven Development (TDD) is a bottom-up, rude(a) approach in the sense that it has picked up its value in the new years. The focus of MDD as the name implies is on the perplexs rather than on enter that guides the discipline of softw argon whereas focus of TDD is on the ravels. on that point have been several changes to MDD since the beginning to deal with the changing environment and complexities raised by projects. TDD started as a partition of extreme scheduleming (XP) methodology and has gained popularity among many developers as a separate practice itself. Traditional, unmanageable cored MDD developers ar accustomed to evolution softw atomic number 18 that seems more indispensable to them considering it to be an engineering approach. TDD developers approach the telephone ci rcuit in a tot in ally different perspective concentrating on customer expectations of the corpse. There are advantages and disadvantages to both approaches. For a high quality software produce that meets the goals of the organization, it is important to go out and apply the most suitable methodology period making certain(p) trade-offs if necessary. The best approach to follow depends on several factor ins including the geek of organization, type of project, and experience the developers have. This paper is aimed at explaining sample driven and strain Driven organic evolution along with parapraxis study and observations. 1. Model Driven Development or MDD.Model stomach be precisely defined as a description of a system from a special(prenominal) perspective, omitting irrelevant detail so that the characteristics of interest are seen more clearly. (Source Patterns Model-Driven Development Using IBM Rational software system Architect) Consider an manikin in which in t hat location is a pressing business need much(prenominal) as automation of certain processes and understanding the data collected in the business. In this situation a Business exists and there are people who are performing certain business activities in certain way. These are the people who are thinking of having a tool or a software product to stand by them increase their productivity and their functionality. These people who are called Domain Experts or compositors case Matter experts or Business Experts know what they want. However, they currently do not have any software product that forget help them to meet their unavoidably. In this situation Domain Experts are the driving force. They do things in a certain way and expect the software product developed for them meet their needs should similarly do things in that manner. However, they do not know how a new software product go forth look alike(p) and how it will help them to meet their needs. People who develop this soft ware product understand the needs, but they whitethorn miss the intricacies of the desired end product. Building a MODEL will help alleviate this situation. A MODEL can be a diagram, an animation or a presentation. If the Software that has to be developed is very petty or involves 1 or 2 people, then the process need not be so ofttimes structured, even though it helps. However, opus developing a large product which will involve tens or hundreds of people having different expertise, regulateling will help them to accomplish this easily. A new product evolution building a Model is absolutely necessary. This is analogous to a civil Engineer creating a model of Building before it is actually built.Model Driven Development (MDD) is a methodology that focuses on invention models at an abstract level without considering the implementation details that guide the development process, focusing on superstar part of the system to manage complexity. Models help to analyze the problem an d visualize the process. Most comm hardly used language for this purpose is Unified cast Language (UML). It establishes certain vocabulary and structure so as to understand and communicate between various developers. Artifacts are produced from the models, so the models are machine-readable, which is an important survey of MDD.MDD is also called as Model Driven Engineering. An implementation of MDD is given by Object Management Group (OMG)s Model Driven Architecture (MDA). digest of MDA is on forward engineering, i.e. creating mark from modeling diagrams. Apart from MDA, there are also other views of MDD such as Domain Oriented scheduling, Agile Model Driven Development, etc. MDA uses platform-independent model (PIM) to describe the system functionality as the first step. Platform Independent Model (PIM) is a generic way of representing the end view of the product without considering any technology or platforms going to be used. This model just transforms the Business requiremen ts into a Model. This format does not contain any fact software compute but carrys the end state of the product in one of the Model development modes such as Diagrams, Flow Charts, and Animations etc. base on the PIM and considering some economic conditions or availability, a proper platform is selected to develop the software. A model is then converted from PIM to platform specific model or PSM. . This contains software scratch at a higher level. Platform is a loose word in this context. This can be referred to type of hardware, software, run system, programming language or combination of any of these put unitedly. That is why choosing a platform is related to economic viability also.PSM can be thought of Developers model where as PIM can be thought of Domain Experts or End substance abusers model.UML representation using IBMs Rational Rose can be considered as PIM. Whereas, tools like IBM WebSphere Studio and Borland Together/J are used for developing PSM. In these, we have CODE VIEW and MODEL VIEW. These two views are synchronized together. When work out is changed in Code View, it is reflected in the Model View and vice versa. The models may contain fixed and variable data, business requirements, presentation elements (forms, reports). If one of these elements changes, they can be incorporated into the model to see the changes that occur due to interdependencies. Based on the affects, 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 (S SAD) is required to develop software establish on Models. In this process, the design (Model) is acceden as the basis to start with the development and as the development process is advanced, it is analyzed with the design and identification number outinged 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 Integration experts. someone should also be able to lean a Liaison role to understand both sides of the table Business side and Software side. This someone 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 subordinated drastically if this Liaison person has good knowledge and is an expert on both sides.MDD is used with many development processes such as waterfall model, iterative model, spiral model, etc. In MDD approach, a model p lays 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 Extreme Programming (XP) approach. Later on, it became a popular method by itself. TDD was originally called Test First Programming. TDD can best be described in three words as Red-Green-Refactor (source Kent Beck). Simple essence of TDD is to write tests before the code is indite. First, unit tests are scripted from the requirements. These tests will definitely fail because the code for it has not been written. In indian lodge to write the tests, it is necessary for the developer to understand the requirements well. Then, code that implements the test cases is written. The code that is written should be just enough so that the tests pass, no more, no less. This means that no guession just some the future story must be made. Test driven approach is then there approach. This means that code is written at that ti me from the user story requirements without making any assumptions or predictions about future. After writing the code, the tests are run and seen if they succeed. If they do, then programmer can be assured that the requirements were met. After this, a process called refactoring is do. This refers to improving the quality 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 running the tests again. This process is ingeminate for the test cases that follow. This process is shown as a flowchart belowSource http//en.wikipedia.org/wiki/Test-driven_developmentThere are different issues to consider in this process. Test cases 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 following condition that specifies the sy stems state, an event that is to be tested, and finally systems state after the event has occurred. Almost either 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 amount of designing that has to be make 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 nearly a year for a good developer to learn most of the techniques in TDD. He divides the learning process in three stages. First stage would take three months to master writing the tests correctly. TDD is a totally different approach to take in developing software and most developers believe that hardest part abo ut it is getting used to it and thinking in that direction. It takes another six months to learn about Mock objects. 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 find many advantages in it. These advantages are explained later in the paper. Pair programming is considered one of the best ways to develop a program using TDD. This is because another person can make sure you are going in right path. It is hard to make developers believe that this approach works. Also, perplexity believes that it is a waste of money to make two people work on one feature small-arm they can 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 Process (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 effective 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 same 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 submit GUI, design, code, tests at regular intervals. The functionalities that had to be implemented included finding the following next date, previous date, zodiac sign, twenty-four hours of the week, next Friday the 13th, number of obtain days left until Christmas. These were each given as a user stories to TDD people. From the impressions of these, the following statistics were madeModel Driven Development approach issuesCr iteriaMDD drug user 1User 2User 3User 4User 5User 6Time To Code (hrs)852898.671117Time to Test (hrs)2151333.32NCSS (non comment source statements) 275600692499280Number of Test Cases 10914251 technology UsedVBA burnt umberJava (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)3493972766542402331095279196298328277Test cases15084124701072471128826256889128TechnologyC.NET VS2008Java JavaJavaVB.Net ExpressCVB .NetVBAJavaJavaVB.NETJavaDecisional Complexity1066676769711562577714581Referential Complexity12434024243419102916029Cyclomatic Complexity118109117100651211498115986115one hundred tenGUInonononoyesnononononoNonoNumber of Times Refactorednone12none5none546113ObservationsEven though t here were well-nigh 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. further 1 out of 12 TDD people developed GUI while all of the six people who did through MDD developed it. One of the reasons 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 quality 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 good developer. Even though the quality and design is neater 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 average 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 w as 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 speculation says that TDD results in highly viscous and loosely 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 minify cohesive nature and 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 eas ier 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 shop days 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 piece of code. Refactoring tells you to remove 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 before 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 instant(prenominal) 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 crusade 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. nigh user stories take less amount of time while others consume lot of time. This can be seen in the case study. Most people verbalize 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 modules which can be assigned to different teams.It helps each team to understand their role and how their part of the development is integrated into the whole product development The project managers and team leaders will understand on how to integrate all the modules and do testing.The end user will be able to visualize the integrated end product.If enough of time is spent in building 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 building 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 audience 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 rudimentary appr oach 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 focusing on one task at a time. Even though it consumes lot of time to write many unit test cases covering 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 wr itten, TDD will result in thorough testing covering all possible paths. If tests are written well, then it will produce stable code.Code is developed faster and there is working 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 leading to modularity and good design. This is also the result of looking at the problem from customers 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 lan guage.The test cases provide support 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 reenforcement management. Developers should be committed and write proper tests. If the tests are deleted or changed accidentally or purposefully, it will give false 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 turn 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. Other tests such as domain testing, integration testing, etc have to be done.Amount 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 chief of when is it appropriate 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 organization, management, type of project, experience of the developers, and availability of effective tools. Type of ProjectSoftware development is done under two major circumstances 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, p eople had thought about having some kind of sharing videos. So, there is direc