2017 Reengineering Project - Mars MIPS Simulator


Mars is a lightweight interactive development environment (IDE) for programming in MIPS assembly language, intended for educational-level use with Patterson and Hennessy's Computer Organization and Design.


Note: Remove all .class files after you extracted the jar archive


A customer wants to use the Mars MIPS Simulator with a different instruction set. The current source code suffers from many code smells and is therefore not ideal to implement such a large new feature. Your task will be to prepare the project for the new feature by refactoring the crucial parts and, in doing so, increasing the code quality. Since we want to be sure that the current features and functionality is preserved, you will have to add some sort of test suite.

In order to work on this assignment, you will need to:
  • Create an account on Bitbucket. An academic account will be provided if you sign up with your university email.
  • Load the source code of the project into a new repository created specifically for this assignment. The team member acting as project leader should create the repository and add the rest of the team members as collaborators.
  • Use this repository as your personal backup and to collaborate with the members of your team.
  • Commit your changes regularly providing information on the activity performed. Any "single" activity that requires file maintenance must be committed as single commit with a simple description of the maintenance perfomed. For instance if you change the system to remove a God Class, your commit would be:

refactoring God Class  or fixing God Class (Extract Class)  or fixing God Class (removing code clones)
if you also introduce new tests:

refactoring God Class + new test added

It is not considered a good practise to commit a big chunck of modified files without providing a reason that explains why those files have been modified.

  • Be sure to commit the final version of your reengineering process. The final commit will be considered for evaluation as part of your assignment submission.
You will also need to send an e-mail to Serge Demeyer and Brent van Bladel with:
  • Object [Reengineering Lab 2017 - Mars]
  • Who is your group composed of? (it is encouraged to work out the assignment in a group (2-3 people)).
  • If you chose to work on a different project, then you will need to motivate why this project would allow you to demonstrate your reengineering skills.
  • Lastly, you have to give access to your bitBucket repository to Brent van Bladel (bvanbladel). 
Then, more specifically, we ask you to perform the following activities, and report about these in your project report:


[Design recovery]

  1. Describe the current design of the implementation of the selected feature in Mars. Clearly indicate how this design is located in the architecture of the project.



    Compose a generic design that describes how the new functionality / feature should be integrated and how the design handles the interaction with the rest of the system. It should be clear that, in a) the types of changes recorded can be easily extended; in b) the choice for a specific storage format is merely an implementation detail; in c) the types of repositories supported can be easily extended.

    It will be necessary to redesign the test suite in such a way that it can cope with the new feature and design.



    1. Estimate the effort required for (i) refactoring towards the new requirements; and (ii) changing/extending the tests.


    1. Refactor the current implementation of Joda Time such that it can handle one of the new features.

    2. Adjust/extend the tests of the project to preserve their effectiveness and coverage during and after refactoring.

You will be required to perform a number of techniques presented during the lab sessions. These are:

  • Analyse:
    • Duplicated Code Analysis
    • Metrics and visualization
  • Restructuring:
    • Testing
    • Refactoring

This project emphasizes the sound, systematic analysis of the presented problem, the associated solution space and the chosen solution(s). The software reengineering sessions are composed in such a way as to prepare you for such a project. We stimulate you to assess the benefits and drawbacks of the techniques presented in the lab sessions, and ask you to exploit the analysis techniques wisely. You are free to use alternative analysis techniques.

What concerns the refactoring-part, we emphasize the use of tests. Our minimum requirements are:

  • Determine the extent to which the current tests provide feedback on your future refactoring-steps. Quantify this.
  • Compose an argument discussing why the tests are (in)adequate for your chosen refactoring scenario, and adjust the tests in case this is required. Be efficient with regard to the time invested in testing.


To show that you have passed the assignment, you will have to demonstrate the following:

  • You have made a selection of analysis techniques (e.g., duplicated code analysis, mining software repositories, metric and visualization as seen in the lab sessions, but others are allowed as well), and have applied these techniques in a sound, systematic manner. You have indicated clearly (using screenshots, results of the interpretation of the output of the techniques) how you have used the results of these analysis techniques.

  • You have performed the above 5 activities (decomposed into (i) Design Recovery; (ii) Design; (iii) Management; and (iv) Refactoring) and discussed them in your project report.

  • The restructurings you have applied are behavior preserving.

    • You can demonstrate the mapping between each of the classes from the original structure with the new structure.
    • The compilation process succeeds flawlessly.
    • The tests run without flaws, and demonstrate clearly that the new userinterface is implemented correctly.
  • The introduction of the new design clearly indicates the project is ready to be released in a language of choice. You are not supposed to carry out the refactoring process completely. Select and execute a set of refactorings that sufficently illustrate your proposed solution.


Aspects that we typically like to see addressed in the report are:

  • Context: Briefly discuss the context in which you are running your project.
  • Problem at hand: Clarify the problem at the base of the project, and indicate its intrinsic difficulties.
  • Project management:Demonstrate how you have organized the work, and how you are controlling it (instead of the work controlling you!)
    • Scope: What are the boundaries of your project? What is not included in the project?
    • Risks: Which risks were envisioned, and which have been mitigated? What is the priority of the risks that still need to be mitigated? E.g., which external dependencies might have an affect on your outcome? Which alternatives have you prepared in case this risk instantiates?
  • Software reengineering:
    • Tests: How can you verify that you satisfy the requirements? Which testing strategy have you selected, and what are the arguments for this selection? How confident are you that your solution satisfies the requirements?
    • Quality assurance: What are the non-functional requirements? E.g., how do you differentiate between a good and a bad solution?


Note: similar to previous years, it is once again possible to submit your own project proposals. These proposals will be approved in case they provide a well-structured exercise on the reengineering techniques presented in the lab sessions. E.g., you can always propose to reengineer another software system, for instance the software system used in your thesis, or written for another case.