COMPSCI 230 S2C 2012 Software Design and Construction

1. COMPSCI 230 S2C 2012Software Design and Construction Revision

2. Learning Outcomes for the Testing Unit • Demonstrate a “theoretical understanding” of testing • Discuss the role of testing in “famous failures” (Ariane, LAS, INCIS) • Evaluate a test suite, with reference to Myers’ principles (“A” level) • Competently perform some test-driven development tasks • “B” level exam questions: write a unit test, specify a test suite, ... • Homework, tutorials: some experience with JUnit and XT. • Demonstrate a basic understanding (by defining or using) the fundamental concepts and standard terminology of software testing • Validation testing, defect testing, unit test, component test, system test, XT, XP, … (“C” level) Revision

3. Learning Outcomes: Concurrency • Demonstrate a “theoretical understanding” of multi-threaded computations • Hand-execute a simple multi-threaded program (“B” level) • Analyse a program to discover consistency and visibility defects (“A” level) • Competently develop, maintain, and test a multi-threaded program • Modify the threading behaviour of a simple program e.g. primeRacer in A2 (“B” level) • Accurately diagnose a deadlock condition (“A” level) • Demonstrate proficiency with the basic concepts and vocabulary of concurrency in Java • Be able to define and use common terms and keywords e.g. volatile, mutex, synchronization (“C” level) Revision

4. Detailed Goals (from lecture slides) • [T1] Develop a “working understanding” of Myers’ definition of “software testing”. • Memorisation is rarely helpful in practice, unless you can apply what you have memorised to a novel situation. • It’s easy to test someone’s memory; testing their understanding is more difficult (and error-prone). Even so, that’s what I’ll be testing: can you “apply” Myers’ definition to some novel situation? • [T1] Help you develop a strength in “active learning”. • I’ll teach-by-example. I won’t test this directly, but if you’re not actively learning I doubt you’ll develop much “working understanding” of anything I’m teaching – including active learning! • [T1] Develop a working understanding of test cases, including the rudiments of test-case analysis. Revision

5. Detailed Goals (from lecture slides) • [T2] Develop a “working understanding” of Myers’ theory of the psychology and economics of software testing. • Can you imagine being interviewed for a job as an entry-level software tester? Would you want this job? • [T2] Develop a test suite for some code without looking at it. (Black-box testing.) • What are your initial questions? (Have you written some already?) • Should I try to “write it myself” (to discover some likely bugs)? • Should I carefully test interfaces, exceptions, or error returns, or should I concentrate on confirming the correctness of functional “internal” behaviour? Revision

6. Detailed Goals (from lecture slides) • [T3] Develop a test suite for some code after looking at it. (White-box testing.) • What are your initial questions? (Have you written some already?) • Should I analyse the specification carefully, as in black-box testing, to discover “what the code should be doing”? • Does white-box testing have an advantage, over black-box testing, in testing “what the program is not intended to do”? • Should I carefully test interfaces, exceptions, or error returns, or should I concentrate on confirming the correctness of functional “internal” behaviour? • [T3] Start to develop your own “principled approach” to software testing. • Do you agree with all of Myers’ principles? Do you have any additional ones? • Do you understand Myers’ argument for each of his principles? Revision

7. Detailed Goals (from lecture slides) • [T4] Have a working understanding of Myers’ principled approach to software testing. • Given some information about a testing situation, can you apply Myers’ principles? (“What would Myers do in this situation?”) • Under what conditions are Myers’ principles inapplicable or inappropriate? • (Note that I’m asking you to write some “test cases” for Myers’ principles – considering its “unexpected inputs” as well as the inputs he explicitly considered! ;-) Revision

8. Detailed Goals (from lecture slides) • [Mutu-Grigg] What is the “real world” of software testing? • Why testing is important • What are the benefits of testing (which may justify its costs)? • Thinking outside the square • The project management triangle • Common forms of testing Revision

9. Detailed Goals (from lecture slides) • [T5] Have a working understanding of XP (as explained by Myers). • Given a description of a software development process, discuss its conformance with XP principles. • What are the major arguments for XP? Against it? • Name, and briefly describe, some of the 12 core practices of XP (as explained by Myers). Revision

10. Detailed Goals (from lecture slides) • [T6] Have a working understanding of XT (as explained by Myers). • Given a description of a software testing process, discuss its conformance with XT. • What are the major arguments for XT? Against it? • Given a development scenario, discuss whether XT could be applied. If it is applicable, what benefits might be expected from its use? Revision

11. Detailed Goals (from lecture slides) • [T7] Develop black-box unit tests from a unit specification • Input validation • Boundary-value analysis • Automate tests using JUnit • This lecture: theory • In tutorial and lab assignment: some practical experience Revision

12. Detailed Goals (from lecture slides) • [T8] Schadenfreude (pleasure derived from the misfortunes of others), with some lessons learned: • Software professionals are trusted to “do the right thing” and to “do no harm”. But we aren’t completely trustworthy: we all make mistakes, and some are unethical. • Safety-critical software can fail catastrophically, even if it is carefully tested. • Enterprise software: failure modes are complex, with no single “cause”, but technical factors are often important. • [T8] An overview of the ACM Code of Ethics • What would you do, if you were pressured to “sign off” on a test report for a system that you aren’t confident will be “safe to use”? • What other ethical conflicts might arise in your professional workplace? Revision

13. Detailed Goals (from lecture slides) • [C1] Develop an appropriate “mental model” for multithreaded programs. • Predict the outputs of a simple multithreaded program. • [C2] Understand why multithreading is important – and difficult! • List, and briefly discuss, some of the ways in which multithreading is used in Java. • Recognise some common “design patterns” for multithreaded computations: Model-View-Controller, simulation with one-thread-per-actor, foreground/background computations. • Explain how a volatile variable differs from a non-volatile one: what are its advantages and disadvantages? Revision

14. Detailed Goals (from lecture slides) • [C2] Refine your understanding of threading: • Make a careful distinction between the support of an operating system (or a computer) for running a thread, and an instance of a Thread object in the execution of a Java program. • [C2] Understand the “lifecycle” of a thread • Start to analyse a multi-threaded application, by identifying “where” in the code the state of a thread can change state i.e. are created, become runnable, start to wait, stop waiting, and are terminated. Revision

15. Detailed Goals (from lecture slides) • [C3] Distinguish daemons from user threads • How are they different? What are they doing in your JVM? • [C3] What are some of the common uses of multithreading in Java? • What is the “thread architecture” of AWT/Swing? Which tasks belong on which thread? What can happen if the EDT is handling tasks that belong on the model or controller thread? • What is a TimerTask, an RMI, a servlet, and a JSP? When might I want to use these libraries in Java? • [C3] Develop a working understanding of synchronization • What are locks? Atomic operations? Synchronized methods? When should I use them? • What can happen if an application has defective synchronization? Revision

16. Detailed Goals (from lecture slides) • [C4] Develop a stronger understanding of synchronization in Java. • Be able to analyse codes with a small number of interactions between a few threads, answering the question “what execution traces are possible?” • [C4] Learn the syntax for synchronized methods • What are the disadvantages of this “syntactic sugar”? • [C4] Learn an important design pattern: using a final instance of a collection to synchronize its methods. • A simple example: a thread-safe cache Revision

17. Detailed Goals (from lecture slides) • [C5] Have a solid understanding of synchronization • Learn a new word and a new concept: mutex, and mutual exclusion • Work through a few more examples • Know Goetz’s advice on when to use, and when not to use, synchronization. • [C5] Be able to diagnose a deadlocked system • Note: deadlock avoidance is beyond the scope of CompSci 230. • [C5] Start to develop your own position on the relative importance of designing for features, correctness, security, and performance. • Agility and maintainability may be more important than some of the above… remember XP? • Consider taking Goetz’s advice and my advice, then decide for yourself! Revision

18. Detailed Goals (from lecture slides) • [C6] Learn some more Java: • wait(), notify(), notifyAll(), thread priorities, thread groups, Thread.UncaughtExceptionHandler(), SwingUtilities.invokeLater(), SwingUtilities.invokeNow(). • Know when and where to use these methods. • [C6] Know the rough outlines of Goetz’s advice on dealing with interruptedException(). • [C6] Confirm your understanding of multi-threading in Java • Summarise what you learned from Goetz’s introduction (and from my presentation of it) • Start to prepare for graduation: you don’t really need me to learn other advanced features of Java, do you? Revision

19. Detailed Goals (from lecture slides) • [C7] Know the rough outlines of Goetz’s advice on dealing with interruptedException(). • [C7] Confirm your understanding of multi-threading in Java • Summarise what you learned from Goetz’s introduction (and from my presentation of it) • Start to prepare for graduation: you don’t really need me to learn other advanced features of Java, do you? • [C7] A brief introduction to executors, tasks, concurrent collections, and synchronizers. • You’ll know, roughly, what they do. This is just an introduction! • You won’t know how to use them well. • You will have some ideas on what (and how!) you’ll have to read & study, if you want to learn how to use these well. • [C7] Start to develop your own point of view on the importance of learning low-level “assembly language”. • You’ll usually be programming in high-level constructs, so you don’t really need to know the low-level stuff. Or do you? Revision

20. Detailed Goals (from lecture slides) • [C8] Work through most of the “Concurrency in Swing” tutorial at http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html • Know how to use the three types of threads in a Swing app • Develop a vague understanding of how background tasks are controlled in Swing (but you won’t know the names of methods, or their detailed semantics) Revision

21. Exam Skeleton Question 1 [11 marks]: Inheritance Given a super class and an interface…, complete the following subclasses … Question 2 [4 marks]: Inheritance Question 3 [11 marks]: Polymorphism Consider the following classes … What is the output of the following code fragment … Question 4 [6marks]: a) What is the difference between …. And ……? b) … Illustrate with an example. Question 5 [6 marks] JTable a) Complete the… b) Complete the… Revision

22. Exam Skeleton (cont.) Question 6 (15 marks) Concurrency Consider the following class: ... a) Assume that two threads are concurrently invoking ... b) Would this class be thread-safe if ... c) Assume that each thread of a multi-threaded program constructs a single instance ... Question 7 (14 marks) Testing In the answer box below, write JUnit test cases for ... import junit.framework.TestCase; public class XxxTest extends TestCase { public final void testYyy() { } } ... Revision

23. Exam Skeleton (cont.) Question 8 (11 marks) Testing. a), b), c), d) are multiple-choice or true-false questions. 2 marks for a correct answer, 1 mark for a brief explanation of your answer (for questions a, b, d) Question 9 (12 marks) Concurrency. a), b), c), d) are multiple-choice or true-false questions. 2 marks for a correct answer, 1 mark for a brief explanation of your answer. Question 10 (10 marks) Concurrency. a), b), c), d) are multiple-choice or true-false questions. 2 marks for a correct answer, 1 mark for a brief explanation of your answer (for questions b, d) Revision