What is software design?

Michael Feathers has a recent blog "It's All Design" where he says:

When I think about what we do in software development, I find it hard to imagine similar things happening in other fields.

He goes on to speculate that an auto designer would never be given a requirement such as there must be fifteen drink holders. I think he's wrong and that we operate in the same way as in many other fields. Come on, there really are vehicles with fifteen cup holders and I can't imagine any auto designer doing that without such a requirement.

In the comments Michael says "I try to imagine what happens in conversations with architects.". Well my wife has a degree in Architecture, but worked in the field only briefly before moving into software development. She has found great parallels between the work in both fields. We are currently working with an architect to design an addition to our house and one of the first things our architect did was ask about any features and requirements we had in mind.

Don't get me wrong, I agree that software development is just one big design process. I really hate how the software development process is so often compared to a manufacturing process. In software the manufacturing is not the development of an application it is copying that application to a disk. What we do, even the lowest level coding, is design not manufacturing.

But I don't agree with Michael Feathers that requirements and design are the same thing:

Maybe requirements is just a word that we use because we're dividing our design work between two groups.. a group that determines the higher level design (what the product will do); and the lower level design (how the product will do it).

Requirements frame design but are the same as design. Something like a performance requirement does not say anything about the design of a product. Software development is a design process and requirements are part of the process, but a stating a requirement is not the same as making a design decision.

"Mocks Aren't Stubs" Revisited

Reading the book "xUnit Test Patterns: Refactoring Test Code" made me take another look at Martin Fowler's 2004 article "Mocks Aren't Stubs". I'm glad I did because the article has been significantly updated (it's practically a rewrite and nearly twice as long) to reflect new thinking about mock objects. The first thing I noticed was the new terminology that is consistent with the "xUnit Test Patterns" book. The second thing I noticed is the new ideas about the different styles of using mock objects. The updated article is definitely worth a read or a re-read.

It looks like we are beginning to develop a shared language around unit testing, like what happened with refactoring and design patterns. It's interesting to watch this kind of thing as it matures and we learn more. It reminds we of how much object oriented development has changed over the last twenty years.

Java Mock Object Frameworks Reviewed

I've been reading the book "xUnit Test Patterns: Refactoring Test Code" so you are going to get a few posts on unit testing. The book is huge, 27 chapters and 944 pages, and packed with useful information. This clearly was no hastily compiled book, the author has invested a lot time and effort. The book has a website here. Right now I'm reading the chapter on "Test Doubles", what you and I would probably call mock objects, but the author classifies into five types: Dummy Object, Test Stub, Test Spy, Mock Object, and Fake Object. The classification is sensible and really makes you think about how you use mocks and stubs. I've been using mock objects for years and never really thought that much about it.

Despite using mock objects for years, I haven't kept up with the the mock objects frameworks. Until recently I've been using the original static mockobjects.com libraries and had not tried any of the dynamic mock frameworks like DynaMock, EasyMock, or jMock. I've finally gotten tried of writing custom mock objects and decided ti was time to try something new. Over the last couple weeks I've been testing EasyMock, jMock, and rMock. So here are my thoughts on the those frameworks.

EasyMock 1 (Java 1.3 or 1.4)

EasyMock uses recording to set expectations. A mock instance is created and the expected method calls are specified by method calls with the expected parameters.

• Documentation is decent and better than other v1 kits.
  
• Includes a tutorial with source code.
• Generally seems simpler than the others to understand.
• Some extra code, instances of the control and mock instance for each mock.
• Need calls to the replay and verify methods for each mock used in a test.
• Recording expectations using actual method calls is an easy to understand metaphor.
• Specifying return values is not so easy to understand. I thought it clashed with the recording model. The inconsistencies with the model of recording of expectations makes things harder.
  
• Had to record method calls, using null values, even when I did not care about what parameters were used to invoke a method. It seems like this would make it harder for someone else to understand the intent of the test.
  
• Less proxy casting than jMock, but two variables are needed for each mock. Need the mock and a a reference to the interface that the mock implements.
• Tests extend standard JUnit TestCase.
  

jMock 1 (Java 1.3 or 1.4)

jMock uses expectation specification and essentially implements it's own little language for setting expectations on a mock.

• Documentation is ok, but could be better. There are lots of classes so it can be hard to figure out where to look for something in the Java Doc. The tutorial is not included in the download. There is no full example with source code.
• jMock Usage is very consistent across all aspects of setting expectations and return values.
• Expectation definition at first seems verbose, but needs fewer lines of code than EasyMock. Expectations and return values are specified together which can make them easier to read and understand.
  
• Method names are specified as strings and may hamper refactoring.
  
• Casting proxies is annoying.
• Tests must extend MockObjectTestCase.
  

rMock 2 (Java 1.3 and up)

rMock follows the same model of recording expectations as EasyMock.

• Quite a bit of documentation, but it was not as useful. Had to generate my own Java Doc. No source code examples are included.
  
• This framework seems to want to totally redefine how unit tests are written. It implements a whole new assert framework which I found confusing, but it does work with JUnit.
• No advantage over EasyMock.
• No special support for JUnit 4 features or Java 5+.
• Tests must extend RMockTestCase.
  

EasyMock 2 (Java 5 and up)

This is a nice upgrade from version 1.

• Documentation the same quality as version 1. Includes a tutorial with source code.
• Much improved over version 1.
• Less code than version 1, no control objects, no proxy casting.
• Does require static imports for the cleanest looking code. More static imports than jMock.
  
• Still requires calls to replay and verify methods for every mock in a test.
  
• Still relatively the simplest to understand.
• Same inconsistencies in the model between recording expectations and setting return values as the previous version.
• Tests extend standard JUnit TestCase.
  

jMock 2 (Java 5 and up)

This is a significant upgrade that I found much easier to use.

• Documentation is better. The tutorial is not included in the download. Still no full source code examples.
  
• Less code, no proxy casting.
• Does require static imports for the cleanest looking code.
• Model is more consistent and simpler.
• The syntax of expectation setup needs a little getting used to.
• All mock variables must be declared final.
• Seems to have the best features of record and play back without the inconsistencies.
• Tests no longer have to extend MockObjectTestCase. Extending MockObjectTestCase is probably still the easiest thing for JUnit 3.
  

While I prefered JMock, EasyMock is also an excellent framework. Either jMock or EasyMocl would be a good choice. I do not recommend rMock. The choice between EasyMock or jMock will come down to personal preference and perhaps the skills of your developers. I think the slightly steeper learning curve of jMock is worth it for the consistency of its model. I was pleasantly surprised at how much easier jMock 2 was to use over jMock 1.

New Version of Cobertura Code Coverage Tool Released

This is not exactly new, but version 1.9 of Cobertura is available. It's not a big update but is worth getting just for the improvements to the branch coverage reporting. I found the branch coverage of no use at all prior to the 1.9 release. Now it is one of the best features. Instead of marking an "if" statement as 100% covered when the "if" block was never entered, Cobertura now requires all conditions to be tested for 100%. The html report even has a nice context popup that tells exactly how many conditions have been tested.

Version 1.9 is a seamless upgrade. I was able to drop it into our builds without any changes to the Ant scripts.

Recommended Books

Here is a list of the top books on various software development topics I recommend. Believe it or not, I've read all but one or two of them, which should give you a hint as to how long I have been doing this.

Design

"Object Design: Roles, Responsibilities, and Collaborations"
by Rebecca Wirfs-Brock, Alan McKean

This is one of the best books on object oriented design you will find. This books focuses is on using approach to object oriented design.

"Domain-Driven Design: Tackling Complexity in the Heart of Software"
by Eric Evans

This is an amazing book and still a favorite. This book explains how to model the problem domain knowledge and create a ubiquitous domain language.

"Object Thinking"
by David West

This is a quirky book and I suspect it won't be to everyone's liking. But for serious OO designers it is well worth reading and full of thought provoking ideas and opinions.

"Head First Object-Oriented Analysis and Design: A Brain Friendly Guide to OOA&D"
by Brett D. McLaughlin, Gary Pollice, Dave West

A gentle and entertaining introduction to the subject. This book will is mainly aimed at novice designers and will probably bore more experienced developers.

"Design Patterns: Elements of Reusable Object-Oriented Software"
by Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides

What is left to say about the book that started the design patterns movement other than every serious developer should read this book at least twice. Just please ignore the Singleton pattern.

"Agile Software Development, Principles, Patterns, and Practices"
by Robert C. Martin

A great book with lots of example code that really lays out some key OO design principles such as DRY (Don't Repeat Yourself). Though I thought the bowling example was a bit weak and I told Robert Martin so.

"UML Distilled: A Brief Guide to the Standard Object Modeling Language, (3rd Edition)"
by Martin Fowler

You won't find a simpler, shorter, or more readable introduction to UML anywhere.

Development

"The Mythical Man-Month: Essays on Software Engineering"
by Frederick P. Brooks

Who would have thought this book would still ring true after so many years. This is a classic that you really ought to read.

"Extreme Programming Explained: Embrace Change, (2nd Edition)"
by Kent Beck, Cynthia Andres

Kent Beck is arguably the leading voice for agile development and this is the book that started it all. A must read for any anyone interested in agile software development. Sadly, so far I've only read the first edition.

"Lean Software Development: An Agile Toolkit for Software Development Managers"

"Implementing Lean Software Development: From Concept to Cash"
by Mary Poppendieck, Tom Poppendieck

Having trouble convincing your management that agile software development makes sense? If these two books don't help then nothing will.

"Waltzing With Bears: Managing Risk on Software Projects"
by Tom Demarco, Timothy Lister

Another classic that still works. If you only read one book on software project risk this should be it.

"Software Configuration Management Patterns: Effective Teamwork, Practical Integration"
by Stephen P. Berczuk, Brad Appleton

This book will help you move beyond simple check-in an check-out to managing your project's artifacts. It explains the proven SCM patterns and practices needed to succeed.

"Pragmatic Version Control Using CVS"
by Dave Thomas, Andy Hunt

An excellent concise introduction to version control in general and CVS in particular. This is a great book for the new or inexperienced version control user.

"Continuous Integration: Improving Software Quality and Reducing Risk"
by Paul Duvall

This is a very good book. Ever since Martin Fowler's seminal article on the subject we've badly needed this book. I only wish it had been written a couple years earlier. This book will be most useful to those new to the concepts of "Continuous Integration".

Programming

"Refactoring: Improving the Design of Existing Code"
by Martin Fowler, Kent Beck, John Brant, William Opdyke, Don Roberts

This is the bible on refactoring. If have not read this book and think you practice "refactoring" then think again. Refactoring, along with unit testing, are key techniques of agile development.

"Refactoring to Patterns"
by Joshua Kerievsky

This book is about using patterns to improving existing designs of existing code bases.

"The Pragmatic Programmer: From Journeyman to Master"
by Andrew Hunt, David Thomas

This is a must read for every programmer. It is full of all sorts of techniques for improving your craft. Ever wonder why the best programmers are 10 or 20 times more productive? It's probably because they are already use the techniques in the book.

"Working Effectively with Legacy Code"
by Michael Feathers

Strategies for fixing that crusty old untested legacy code.

"Code Complete"
by Steve McConnell

I first read this book twenty years ago. The newest edition is just as good a guide to the why and how of writing great code as the original. This should be on every programmer's bookshelf.

Java Programming

"Pragmatic Unit Testing in Java with JUnit"
by Andy Hunt, Dave Thomas

You won't find a better tutorial on unit testing or JUnit. Give this book to any programmer new to developer testing.

"Effective Java Programming Language Guide"
by Joshua Bloch

Every Java programmer must read this book! Any Java programmer that hasn't should not be allowed anywhere near a Java compiler.

"Java Generics and Collections"
by Maurice Naftalin, Philip Wadler

A clear guide to a tough subject. I think everyone will learn at least one new thing.

"Thinking in Java (5th Edition)"
by Bruce Eckel

Architecture

"Patterns of Enterprise Application Architecture"
by Martin Fowler

"Enterprise Integration Patterns: Designing, Building, and Deploying Messaging Solutions"
by Gregor Hohpe, Bobby Woolf