Agility and legacy code refactoring

Let's say you have some bad legacy code (I have yet to see a codebase without any,...). When, how should you refactor/reengineer it?

In an agile context, there are conflicting forces related to that matter:

• deliver as much value as possible
• have a unit test for each line of code
• refactor mercilessly
• raise your velocity

Real cases from real life

Ok, this is very abstract, let's take some real cases:

1. You need to implement a cache to lower memory consumption (this is the consequence of a customer request) and you realize that the objects you are building are not properly build:

instance = new Model(xmlContent);

Creating a model doesn't have to be dependent on a specification representation format. You'd better use a factory for that. This code should be refactored,... But is it the right time to do so?

2. You found the fix for a nasty bug. Very very nasty, ... But deeply buried in a horrible mess of interactions. You have to write a unit test to correct the guilty class. Easier said than done. A real unit test may require a lot of refactoring, just to untangle the class dependencies.

What should you do? Write an "integration" test? Take time to write a unit test, refactoring everything that's necessary?

3. You have to add a new import/export functionality. However, your persistence design is so bad that implementing the function looks like hell,...

Should you refactor your persistence design? This may halt the team for many iterations. Should implement the function, going through so many loops and hooks, but doing it in a realistic time?

The books/consulting answer

I would like to point out an easy answer from a well known book or website, but I haven't found any. No, wait, there's one! The famous "consultant answer": "it depends,..."

Whose call is it?

Well, before emitting an opinion on the subject, I would like to add some more questions: whose responsibility is it to answer? Is it the client? Is it the team? Should they bargain refactoring actions around the velocity issue?

I think,... (drum roll,...) that this is,... (drum roll again,...) a development team issue. Let me list several reasons for that:

• the team has the responsibility to improve its own velocity
  
• the team has the best knowledge on how to do it
  
• the team has to live with the code day after day and suffer from its sluggishness
• really empowering the team also means letting it decide on how to improve its velocity
  

Now, what can be the policy for the 3 above cases?

Refactorings in the 3 cases

1. The "oh, this should be refactored" case

The pair-programmers should not refactor any code that doesn't get in their way. 3 reasons for that:

• keep the velocity up,
  
• don't risk to break existing working code,
  
• work on that code when really exercising it (so they don't take the risk to over-refactor)
  

By the way, this is such a real case that we incurred a several days development penalty lately for not following this rule (hence the idea for this blog entry,...)

2. The "nasty bug" case

This one is a "must do". You have to write a unit test for your fix, even if it is difficult. If you don't do that:

• you take to risk to face the bug again
• you may write an "integration test" that will slow your test suite and may be very fragile
• you open the door for your QA team to write more fragile validation scripts
• you don't show to path to more testability and better design for the guilty class
  

Having said that, the refactoring can range from a complete reengineering of the guilty class, to the sole extraction of the guilty behavior in a special-purpose class, passing by the only isolation of the bad class.

On that real case, we chose to reduce as much as possible the class dependencies, just to be able to test the fix, and only that.

2. The "new functionality/bad velocity" case

This one calls for a trade-off (the famous "it depends").

On one hand, you cannot spend several iterations on your brand new this-time-I-will-get-it-right-design. On the other hand, adding functionalities on existing debt adds more debt (and we all know about interest rate composition).

The only duty here is to do at least something. You have to set the path for the reengineering of the offensive design: implement a tiny part of the solution and communicate a new vision to the rest of the team.

Then, on any of the 3 refactoring cases, another pair can pick up the new design and push the codebase towards the new path. The net result of this strategy is:

• a velocity that will better reflect the codebase state
• an investment against more debt if not an investment towards a better velocity

This is also a real case,... we chose here to prepare the path for persistency isolation by introducing several abstract classes upon the base class of domain entities to isolate the persistence behavior. Then we have to move some entities to an abstract class with less dependencies.

Let the team clean the house

I think this is very important for the team to communicate a lot here. The first case calls for information: "refactor that, next time you have develop/fix that code".

The second case needs communication around the new concepts introduced to enhance testability or if the extraction that has been done is a bit clumsy.

The third case, presenting a compromise and beginning some kind of pharaonic work around the existing code warrants obviously for a lot of discussion.

It's like house-cleaning,...

• if you don't do it regularly, it can only get worse
• you can fix a broken bulb more easily if you have ready-to-use tools and spare parts
  
• building a new ground-heat heating system is a long project but this will be a nice replacement to your ever-broken old one. In the meantime, you can still add a new remote control, even if it would be easier on the new system.
  
• you have more fun when you appreciate where you live!

[Update 03-08-2006]

Ian Roughley has written a very good article on a non-intrusive technique to write tests for legacy code. Add some logging traces and a Junit appender!

This is a really nice technique to use when you want to fix a bug and don't have time to break all dependencies to write a unit test (or you can't take the risk: see case n. 2).

You can also use it before refactoring some code, but in any case you'll have to get rid of those tests sooner or later (see my comments on the article) to replace them with "real" unit tests.

Unit testing with style

Writing unit tests looks like an art sometimes. You want to:

• test your class functionalities
  
• test it properly in isolation
• convey the specification of the class as clearly as possible

Following those objectives, we encountered today some issues that are most certainly classical but not necessarily handled properly.

Setting-up of an input object hierarchy

Our tested class is a factory that takes an object hierarchy build from a parser and creates another hierarchy of objects.

To make an analogy with an xml configuration file, the first hierarchy is a set of xml nodes and attributes, the second one is a configuration object with specific composed options. The issue is: how do you build the input object hierarchy in a way that's readable and really conveys its expected structure?

The unreadable way would go like that (in java):


AtomParameter attribute1 = new AtomParameter("attribute1");
AtomParameter attribute2 = new AtomParameter("attribute2");
ListParameter classList = new ListParameter();
classList.add(attribute1);
classList.add(attribute2);

AtomParameter class = new AtomParameter("class");
ListParameter modelList = new ListParameter();
modelList.add(class);
modelList.add(classList);


And the readable way goes like:

Parameter parameter = list(atom("class"), list(atom("attribute1), atom("attribute2"));

By implementing the proper 'list' and 'atom' functions (returning List/Atom Parameter) the resulting code conveys the expected structure much more clearly. Unit tests as a software specification gets more real!

Testing in isolation

Not a new subject here, we use jMock to isolate our class. However, here's a pattern we've used some times. Our factory class declares 2 constructor methods:


public static ModelFactory createFactory(Project project);
public static ModelFactory createFactory(Project project, Translator translator);

In that case, the first method uses a default Translator implementation and the second one allows for another Translator, which is going to be our mock object of course. The second method may look like a pure test-only method but if you come about it, it is just extending the Factory API towards more flexibility.

By the way, I would also like to point out in this entry, one of the difficulties with mock objects in general. There is no way to specify the protocol for using an interface in a central place. If operation1() must always be called before operation2() on an interface, the mock expectations won't really declare that. Moreover, the expected protocol cannot be enforced from any unit test where the interface is called.

Protocol errors will then be catched by integration tests (acceptance tests for instance). The creator of jMock, Nat Pryce, has attempted to get around this, but he ultimately thinks this is too complex to do in Java (see the pragprog mailing list archive).

Expressive assertions

JUnit has blessed us with quite a few assertXXX methods but I have recently followed the advice found in this article, and it really changed the way we use assertions.

For instance, testing our factory goes like this:


assertThat(aFactoryUsing(model1).createInstance(parameters), containsSlots("a", "b"));

assertThat is an assertion method from MockObjectTestCase
aFactoryUsing() is a method creating a properly setup class to test
createInstance() is the tested method
containSlots() is a method returning a custom Constraint object (from the jMock framework) and doing the necessary checks for the test

The nice thing that comes for free from jMock is then the ability to compose custom and standard constraints. For instance:


and(containSlots("a", "b"), not(containSlots("c", "d")))

First-class code

At the end of the day, unit testing with style is not wasted time. If you consider your unit test code as first-class code, that must be as factored and expressive as possible, you will really facilitate communication, design and maintenance (especially test code maintainance, which can be otherwise very, very, very expensive,...).

Feedback from another Dojo

Today's Dojo was interesting, at least interesting enough to keep a trace of it.

The subject

I wrote a small Dojo subject a week ago that was selected by the group. The subject was to have a DSL to describe Recipes and to be able to compute some data about it.

Let's take the easy-child-access yogurt recipe:

• Pour one yogurt
• Add 3 eggs
• Add 100 ml of vegetal oil
• Add 200g of sugar
• Mix all with 300g of flour
• Cook during 30' at 180° celsius
  

The idea is to be able to compute:

• the list of ingredients with their quantities
  
• the cooking time
• the preparation time

Of course, you can start with simple calculation rules and add more complex ones such as:

• "Melting 50g of chocolate takes 30'' in the microwave"

You can also play with some grammar aspects:

• synonyms: Add, Pour
• complements: in a jar, with a mixer
• ...
  

I had several objectives with this subject:

• Make people collaborate on a quick design session
• Implement a parser for a DSL

So far, people decided to vote for this subject and we chose to focus on the quick design session then on some coding.

The Quick Design Session

This session was elaborated with somebody at the board during 5 mn, sketching a domain model. We quickly converged on the main classes: Recipe, Action, Ingredient, Quantity and thought about some kind of PreparationTimeEngine that was responsible for calculating preparation time depending on an action and its ingredients.

The acceptance test

We started coding an acceptance test for a very simple recipe: a yogurt with sugar!

• Take 1 yogurt
• Pour 10g of sugar
  

And programming the acceptance test took us the remaining 35' we had on the session,...

The retrospective

Yes, the result was not tremendous, and I am still thinking: "wow, 5 poor classes, 1 acceptance test = 1,5 hour, not a great productivity".

Anyway, I liked this Dojo for what we learned:

• :-) The quick design session pleased everybody because they really had the opportunity to share a common design. Something to do again "live", because this really accelerates the feeling of common ownership
  

• :-) I liked the emphasis on getting the acceptance test as readable as possible and the hunt for local variables that were not necessary

• :-) I liked the discussion around the necessity to have factory methods: createAction,...

• :-) There's no better place to jellify the group around fun and quality code
  

• :-\ Some pair co-pilot were relatively silent. Their role was taken up by the group

• :-\ Yes, I still think the productivity was poor and I think this shows plenty of improvement room for the group

• :-? We should try to enforce the rule that the group is silent and only the pair should talk. The other ones could take notes, observing the functionning of the pair

• :-? I wondered about the use of Java for this kind of Dojo. Python or Ruby would be more appropriate and productive

• :-? It is certainly better to prepare the Dojo subjects, so that the participants can get up to speed in a limited time. I had prepared a written spec with an acceptance test, but written acceptance tests would have been better. I think this is even more true with some of the subjects we wanted to do: Bayesian Filter for spam, Java Plugin Framework,...

Now, let's see how goes the next one.

Responsabilities dilemna

When can you say "too much is too much"?

Let's say you have an object: Customer. Wow, how original! Anyway, please bear with me.

So, your Customer class has some "customer info" responsabilities, but also it may be a "billable customer" or a "prospective customer" (for cross-selling). Hey wait, it can also be a "persistent customer". And so on.

How do you manage all these responsabilities with a classical object-oriented language?

The Horror show

First of all, you could put all the code in the Customer class. Boo-oo! "OO for beginners" tells us its bad, you end up with a 2000 lines class.

or,... you could have only a Customer class containing the customer info and a BillManager that bills a customer, a SellManager that tries to sell him stuff,... No, I'm kidding, let's forget that one too.

or,... you could inherit from a PersistentObject class, derive BillableCustomer from Customer,...

Time to stop the horror show.

Delegation forever

Then you can put everything in the Customer, but it can delegate to other objects. For instance, customer.save() would delegate the real action to a CustomerRepository. This would be the same for other responsabilities.

What about testing? Oh yes, testing,... Ok, you can use your best-of-breed dependency injection framework to inject the proper objects behing finely crafted interfaces.

Right, but what about dependencies anyway !? Your Customer class is still not reusable without a whole bunch of interfaces! What if you don't want your customer to be billable at all?

Ok, you can set the persistence aside by having the Customer clients make calls to an appropriate factory after dealing with the customer. But what can you do with the billing responsability (No, not the BillManager again,...)?

Object inheritance

Another way, suggested by the Streamlined Object Modeling book is to use "Object Inheritance". You use the Actor-Role pattern and define 2 classes:

• the actor: Customer class
• the role: Billable customer class

A billable Customer class will have the same interface as the Customer class and will delegate all customer info requests. We could say this is a kind of "external delegation" in contrast to the "internal delegation" mentioned before.

When discussing this pattern with a friend recently, I told him that I felt uneasy with one thing (beside the heavy use of delegation which results in silly code in Java). It was strange for me to have 2 objects representing the same logical entity.

He told me to consider another way to see things: BillableCustomer would be a "decorator" of Customer. If I need a BillableCustomer, I write: new BillableCustomer(customer) and do my job with it. I really like this way of seeing things. There's still one drawback in my mind: if BillableCustomer needs to be persisted, you still have to consider 2 entities for the same logical object in the system.

Dynamic languages to the rescue

In the end, what I would like to do is to mix behaviour into an object. This is exactly what Ruby allow me to do: I have a Customer class and I can extend it Billable responsabilities at runtime:

customer.extend(Billable)

This is the idea of "Duck typing". You cannot rely on the object type alone to know its capacities. If it walks like a duck and quack like a duck, then it is a duck (even if it is really a swan,...)

There is certainly closer to "object-orientation" than any class-interface-inheritance pattern. If we think of it, object are often thought as human when doing object analyzing. And we, as humans, often learn and forget, get abilities and loose abilities. Objects should be able to do the same.

A new persistence challenge

But "when is easy, too easy?".

Yes, when it comes to persistence, how do you do in Ruby with something like that? ActiveRecord was not thought with that kind of use in mind.

;-) I have no doubt that Rails fanatics could come with a fairly elegant solution to that problem.

Enlightment, planning and convictions

Sometimes, learning new things is scary.

You've just learned something you find very important, acquired a new skill and you ask yourself:

"How can I have worked without understanding something so crucial during all this time?"

Well, another more useful question usually pops up in my head:

"Why was I not able to pick this up before?". This is certainly more useful because it opens up the possibility to pick it up faster next time!

Recently, I got the feeling that I learned very important lessons about the raison d'être of agile methodologies.

The cards array enlightment

I remember standing in front of our cards array contemplating the next iteration planning and the result of our last planning game. I was thinking: "now I know why I was not so effective as a project manager for planning the activity of the project" (better late than never!)

Planning, yes but why?

I always had difficulties for planning software activity, and was even beginning to think that development was something like the butterfly story introducing any chaos theory presentation: a beat of wings and milestones go away.

Many of my attempts to get more insightful plannings failed. Here's a set of recurring issues:

• how can the development planning stay in line with the global roadmap (especially if it is very "ambitious" but also a moving target)?
• how do you plan bugs?
• how can you make accurate predictions regarding the delivery date?
• how do you fight developers natural optimism ("well, 2 days should be ok for the parser")?
• how do you plan non-development time (meetings, holidays, illness,...)?

Moreover, every "aggressive planning" I saw was the recipe for repeated failure. And the effects on the team are disastrous: "Whatever we do, we are late". But "late" relative to what? A release date set by a manager and approved by a developer muttering to himself "I'll do what I can". So what's the real use for a planning?

A manager answer included: "setting a challenge to motivate the developers". This is the "aggressive planning" theory. A really counter-productive one, since it leads to the "We're always late" syndrom, which is soon followed by the "We're poor developers" consequence.

I had my own variant on aggressive planning: "Watch what you do and register time passed". I thought that doing this will drive individuals to be more conscious of "unproductive" time and get rid of it. I was wrong. A developer can chase "unproductive" time only if he has decided to, not if he has to fill a time report precise to the hour (I have even read about minute-precise time report, where bathroom time is to be precised!). And then, as a mean, he can watch his time spent.

So I figured out there must be better reasons for doing plannings (instead of the "I develop to my best abilities, you pick the product when ready" approach).

One of the reasons is resources management. If time-to-market is a crucial issue to the Product owner, then he may wonder "how many people can I add to the project to get it faster?". Once you keep in mind the Mythical man-month essay by Fred Brooks (and this funny anecdot), you can still try to add people to reach the project optimal size.

One other reason, is some kind of control over what is developed. Plan your activity, do the job. If along the way, the plan is not respected, this may be interpreted as a warning. However, if the meaning of the warning is that your plan was not accurate, you have not gained much.

And maybe the most evident reason is the need to communicate dates to people outside of the project: customers, sales representatives, consultants, investors,...

Planning revisited

After our 6 months effort to implement the full agile practises stack (we already had continous integration, unit testing, iterations), I now understand why this works:

• you deliver software in a time-box manner and focus on priorizing customer value, having both short-term control (the iteration) and mid-term control (the milestone)
  

• you have a very simple measure for productivity: velocity. You globally measure the capacity of the team to deliver useful functionality. Meetings occur, bugs occur, obscure technical work occurs but it is not counted as such

• estimations are more reliable because of the planning game. Indeed, estimating a task is better done by a bunch of people having different experience and knowledge about it (I used to do that on one-to-one with the "concerned" developer - which is not a relevant concept in eXtremeProgramming anymore)

• estimations are also more reliable because of the frequency of the planning games (every 3 months)

By the way, I want to emphasize all the benefits of the planning game:

• developers have the opportunity to understand precisely the customer objectives
• the customer can get a better grip on development risks and difficulties
• the team is really empowered and feels responsible for the overall project

Let the team manage itself

The last point is what stroke me in front of the cards array: many brains are better than one.

• the team is much more efficient at organizing the project than the project manager
• the team is much more efficient at defining and estimating the tasks
• the only way to get the maximum productivity is to trust the team members and let them set high-productivity standards. No management indicator can ever imply high productivity. You cannot measure commitment, smartness, collaboration

The consequences for a project manager seem pretty clear to me: you are only here to help the team manage itself.

How to do better next time?

Thinking about that, I concluded 3 things:

• I should have experimented more. Some agile practises seems evident. Continuous integration is one of them (spend machine time instead of developer time). Some other are not so intuitive: why use physical cards to track development tasks? It is not until you hold one in hand that you can feel why

• Empower the team. This is the brain number effect. I also find some relations with Michel Crozier's theory regarding the fundamental liberty of any worker to gain power around him. This also means that team management can never be an easy path

• I should live up to my convictions. For instance, I was not strong enough on emphazising why continuous integration should always be green, no matter what (this one I experimented)

Don't give up on your conviction

We all make mistakes, learn more or less painful lessons. However, when we learn something the hard way, we'd better not forget about it. What we learn become our convictions and the remaining questions have to be experimented.

I recently read a blog entry of an experienced developer analyzing the reasons behind his software projects failures. The whole entry is worth reading and wondering about. But one specific thing was worth remembering for me right now:

And if you decide to make changes, have the courage to go 100% with your gut. I've failed more than once when I watered down my convictions in order to appease dissenters. The only thing worse than evangelizing change and failing is looking back and realized you might have succeeded if you'd held firm on your convictions. What a waste!

I won't be caught twice on that one.

More analytics, less mechanics

The opening keynote of ICSTest Düsseldorf 06 was: "Tools: what we really need and how to get it?".

Mechanical tools

The speaker made an important distinction for testing tools: most of them are "mechanical tools".

• Some of them are just a way to store data and to support a process. They are nothing more than a specialized database.

• Other ones are dealing with the execution of test cases on different machines, with different environments. They are nothing more than a specialized batch file.

• The last ones are experts at interacting with gui components to insert and retrieve values. They are nothing more than a specialized keyboard and mouse simulator.
  

Of course, this is an oversimplification and each of these products is not easy to get right:

• Test management tools must deal effectively with concurrent modifications of shared data, they must provide nice edit and search capabilities, they must support every possible workflow
  

• Distributed test execution tools must help with different hardwares, different OS: reexecuting the same C script remotely on 2 different systems is not straightforward for instance
  

• Graphical test tools must allow the creation of test cases independently of the application-to-be and allow a flexible and evolutive mapping between the test cases and the graphical components
  

But still, this is just dealing with plumbing (see my previous post,...). Any serious attempt at managing the complexity of testing today systems should allow you to:

• get objective information about your actual coverage
• refactor test sequences and extract the common parts
• propagate modifications of the specifications to the test plan
• analyse test dependencies
• generate test cases from the specifications
• propose test strategies from the system typology
• combine components test cases into system test cases
  
• ...

Analytical tools

All these tools would be called "analytical tools". They support the human mind when it is somehow limited:

• exploration of exponential number of possibilities
• analysis of complex relationships
• metrics-based decisions
• exhaustive application of systematic rules

Why are there not more of those tools?

The "low-hanging fruit" rule

The answer is "the low-hanging fruit" rule.

Most of the time, the mechanical tools are easy to implement and bring immediate return on investment. This is why big companies such as Mercury or Borland focus on "process" tools and their integration. Moreover, those tools appeal to the common manager, they tend to give the impression that everything is under control.

You can use TestDirector and feel that you can really manage a fine test plan covering your requirements. But how do you know you've written the right test cases? How do you know you got the minimum number of them for the best coverage?...

By the way, there is a similar argument for the CMM process improvement. You may set up reviews and yet do terrible ones, you may have source control configuration and yet create unnecessary branches, and so on.

In the end, one of the speech conclusions was that the innovative companies should be supported to get greater benefit for special analytic tasks. The answers won't come from the big corps.

Mercury and co. will provide mechanical tools to support your mechanics, innovative companies will provide analytical tools to support your brain!

Back to language roots (and to plumbing once in a while)

I have been musing a lot with computer languages recently.

Parsing Ruby code

First of all, I needed to be able to analyze some Ruby classes and extract part of the operations behavior. For instance, I needed to parse the following code:

if (p1 == 2 && p2 == 1)
@attribute = 3
else
@attribute = 4
endif

I wanted to extract something like:

p1==2 && p2==1 'implies' @attribute = 3
and
not(p1==2 && p2==1) 'implies' @attribute = 4

So I started to write my own parser, that would take the ruby class file and:

-find the class definition
-find the operation definition
-parse the if-then-else-endif expressions (that can be nested,...)
-...

There's got to be a better way!

A better way

Google was my guide to a super ruby library: ParseTree (http://rubyforge.org/projects/parsetree).

ParseTree takes some ruby code and return a "sexp" (symbol expression) that represents the program being parsed. For instance:

def example
1+1
end

becomes

[:defn, :example, [:args], [:call, [:lit, 1], :+, [:array, [:lit, 1]]]]

Then, the ParseTree library offers a Sexprocessor class that allow the easy consumption of the sexp.

This is fine for the theory. The usual practise of a programmer is less shiny:

• I had to download also RubyInline which is a library that allows c code to be compile then called by ruby code
  

• I had to let RubyInline compile the ParseTree c code, which took me some hours to do tweak it right, from modifying part of ParseTree c code to modifying the RubyInline compilation command to work on my Windows laptop (the ParseTree/RubyInline folks don't seem to be willing to live with Microsoft around). If you encounter the same difficulties, send me a mail, I'll try to help you
  

When I do that, I really feel like a computer plumber, there are so many more interesting things to do with a computer! Anyway.

Then I realized that the trip wasn't over: parts of the sexp had to be translated back to Ruby code again!

Back to the roots of programming

This is where I found (or more exactly refound) Paul Graham articles on Lisp (http://www.paulgraham.com). I was really fascinated by the data <-> code equivalence offered by Lisp. The syntax is simplistic and the code is already expressed as a syntax tree!

The funny thing is that the first language I was taught in my engineer school was Scheme, a Lisp dialect. At that time, I mostly saw the power of recursivity, but not this idea of extending the language itself with macros, and so on.

One more funny thing before returning to Ruby: Lisp was not invented as a new language, but more like discovered as an experiment to find another computation axiomatisation than Turing machines (John MacCarthy, 1957!, see Paul Graham's article).

From Ruby to sexp to Ruby again

Anyway, back to Ruby, the idea is to use another Ruby library: Ruby2Ruby (in the zenhacks gem) that should do the trick. I have not yet finished the round-trip experiment, but this should do it. The idea behing Ruby2Ruby is to implement most of the Ruby language as Ruby code, leaving only a few primitives translated to C. This provides some interesting lines of code in the library tests, check it out:

r2r2r2 = RubyToRubyToRuby.translate(RubyToRuby).sub("RubyToRuby","RubyToRubyToRuby")

Good luck with that!

A mini-language for acceptance testing

Today, I wanted to write acceptance tests for our generation algorithms. The trouble is that our algorithms explore a tree of possibilities based of the system behavior. What I would like to do is:

• to specify a pattern of possible behaviors
• having some java code generate the system behavior based on the pattern

Not clear? Let's say I have the following pattern:

[a*|b]*cd. This would mean that, if my system prints a, b, c or d letters when stimulated, then the printed string must follow the [a*|b]*cd pattern.

So, rolling up my sleeves, I first tried to implement a parser for those types of expression. Again, implementing my own parser? There gotta be a better way!

A better way, revisited

I thought about JavaCC, Antlr and then I recalled an article about JParsec. JParsec is a port of the Parsec Haskell library. The main difference of JParsec with JavaCC and Antlr is that it is not a code generator. You do not feed it with a grammar and get back a parser for your (mini?)language.

So I tried to define my mini-language parser with Jparsec. Unfortunately, I got stuck by the lack of available documentation (the codehaus server was down all day long, it still is). At the end of the day, it looked like I was back to plumbing again, having a library and using it as a blind man with trials and errors.

Perseverance, mini-languages are a must-have

I should many collect writings on the qualities needed to be a good programmer. Perseverance seems to be one of those. It would be very tempting, in my situation, to let down the JParsec trial and to write my own parser. Or to let down the whole mini-language idea and to write ad-hoc acceptance tests.

However, I feel that perseverance here is important. Mastering the creation of mini-languages is such a powerful tool in your toolbelt.

Because the best way to leverage the assembly language was to create a programming language, the best way to leverage a programming language is to create mini languages that are adapted to your domain.

Build up on your own language

Related to parsers and the use of mini-languages, I would add a concluding thought: every computation should be done within your programming language.

This is why I like Ruby and Rails.

This is why I don't like java AOP: when you use java AOP, the syntax is specific for the annotations, you have an extra "weaving" pass in your development process.

In the end, this is where Lisp may be leading us (or only me?): parsers and code generators should be included in the basic toolkit of any decent programming language and every programmer should master them.

Funny recruitement ad

We were writing a recruitement ad yesterday and were thinking about the kind of skills and experience we wanted for 2 senior developers.

My colleague showed my the web site of a guy presenting himself as Erlang code. This was really funny and I had the idea of writing acceptance tests for the ad!

It went like that:

public class CandidateAcceptanceTest extends TestCase{
Developer candidate;
public void setUp(){
candidate = new Developer();
}

public void testTechnicalSkills(){
assertTrue(candidate.isJavaExpert());
assertTrue(candidate.knowsJDO());
}

public void testMethodologySkills(){
assertTrue(candidate.canTeachAgileMethodologies());
..... and so on
}

We were even arguing about how writing the acceptance tests that would best describe the "optional" skills: the ones that were desired but not mandatory.

The result was indeed quite interesting because I thought: the guy (or gal) that will read this ad, understand it and like it should be on the right track for the job!

Dynamic languages are scary?

I have noticed a post on the Ruby on Rail mailing list that catched my attention today:

> I somewhat agree with you, but I recently
> realized I don't even know *why* I feel that way. Is it because
> dynamic scripting languages, by being way less chatty than something
> like Java, somehow feel more fragile? I seriously wonder.

It was about implementing financial transaction systems with Rails.

This thought catched my attention since I have been programming a lot on my free time recently with Ruby (as an attempt to prototype some ideas that I found revolutionnary for our product).

While programming, I had many times the impression that I would accidently misname a variable or a method and that my program would fail at run-time. No more compile-time safety. This is like jumping from a plane without knowing if your parachute will open at the right time. And this really made me feel uneasy.

Think about it: you program in java with Eclipse or whatever advanced IDE. Every class name or method name can be safely completed, researched, refactored,... This was a real advance for day-to-day programming. With Ruby, or Python, this is all gone. Scary, isn't it? How can you build large systems, knowing that a single mistyped name could bring the whole system down without you even knowing it right now!?

I was indeed scared! However I could also recognize that I had been able to program a quite complex infrastructure in Ruby that was doing the job! So, what are the keys to more confidence in dynamic languages?

The keys to get more confidence are interesting since they are anyway the foundation of better development practises.

TDD virtous circle

I have been practising TDD for this project, I have been checking my coverage (with rcov) all along and I have paused enough to consider refactoring each time the tests were green.

So the first key is "start the vertuous circle of using TDD". You can start using TDD, just because you're afraid to break anything, anytime. The added benefit is a Test Driven Design.

Ruby is your best refactoring friend

The second key is "use Ruby capabilities to refactor to the maximum". Ruby on Rails has really shown that "less is more" and that duplication could be avoided up to the limit. Most of this magic is done thanks to Ruby. Ruby helps factoring code well beyond what can be done with Java (without AOP and all that metadata stuff). The added benefit is a readable code, aiming at representing the domain and nothing more.

Good engineering is here to stay

The third key is "use your object and architecture skills". Whatever the language, if you design carefully your system, with encapsulation, delegation over inheritance, layers, patterns,... you should end up in a system where undesired effects can not ripple too far. The added benefit is a maintainable and evolvable system.

Fragility turned into strength

So, basically the lesson here is that Ruby (and al.) fragility practically forces you to sign for sound development practises. You get more confidence in your development and the added benefit is that you develop it faster!

Fitnesse and Rails : bridging the business/technology gap

I have been so far quite enthusiastic with 2 frameworks: Fitnesse and Rails.

Fitnesse: executable specifications for the developers

Fitnesse is a framework that allows you to create HTML specification pages in a wiki. Those specifications can include any form of text, images and HTML links. But they can also include tables that specify acceptance tests for your system.

Then, provided that a developer (or better: a pair of developpers,...) has provided a "fixture", that is, a java class that will implement the table, the HTML page is executable! Once executed, the page shows the expected/actual results and uses the famous green/red colors to display those results.

I see many advantages to this approach:

• The HTML pages look like a classical specification to the analyst
• Having the analyst specifying very precisely expected values results in much better specifications
• This makes the analyst and developer discuss very precisely the requirements and their possible implementation (when creating the fixtures)
  
• This forces the analyst and the developer to think about the testability of their system, which usually results in better designed systems
• This is the start for a global Test-Driven approach to system development

There are still some points that could be improved:

• The wiki markup language itself is weak and would really benefit something like Confluence (if Atlassian guys hear me,...)
• The integration into a continuous build system is not standardized (with an ant task for instance)
• The implementation of some concepts is not first-class (try to add something like ${myVar} in a table,... Fitnesse will try to evaluate it, even if it is in fact part of your specification)

Anyway, this is the first time that I come across really useful and not deprecated specifications, which is quite uncommon in the industry.

Rails: a bliss

It is hard not to come up with glorious adjectives when speaking about Rails. I have not been specifically a web application developer knowing all the nitty-gritty details of web application development: urls, sessions, security, html specifics, javascript,...

And Rails makes it so easy. Each time I asked myself: "how can I do that"? I found an elegant solution in the Rails framework. And when I dont find it, I think "I have to search harder,..."

Of course, part of the success of Rails is due to Ruby, enabling beautiful code with minimum of syntax. I have been, for instance, very easily refactoring some test code by intercepting calls to my tests methods to assert the same thing in several methods.

There are 3 other reasons in my mind:

• the famous "convention over configuration". Having nothing to do when implementing the default/most common behavior is productivity at its maximum
• the dynamic aspect of the language: you don't have to redeploy to see the changes
• the people that designed the framework really know about web application specifities. And they did their maximum to leverage Ruby and the DRY principle (Dont Repeat Yourself) to reuse this knowledge

All this gives a very fast track to implement business rules and applications.

I am really wondering what is going to be the success of Ruby and Rails in the next years. Certainly Java won't die (21st century cobol), but what I know for sure is that Ruby and Rails is really fun and productive to program with.

Those are 2 really strong arguments for people with squared fingertips !

Relationships as first-class citizens

Here is a link to a research project for having relationships as first-class citizens in Java:

http://www.cl.cam.ac.uk/%7Eaw345/talks/ecoop05.pdf

Not a new idea, the article mentions another dating back from 1987:

• J. Rumbaugh. Relations as semantic constructs in object-oriented development. (OOPSLA 1987)
  

This is for sure a topic that will make its way to a programming language someday. However, the above article indicates that this is a tough subject and that many of consequences of having relationships as first-class citizens are not yet mastered: inheritance, multiplicities, construction,...

I would bet that adding this kind of functionality via a mixin in Ruby could be a great way of getting the details right, in the manner of what is been done for ActiveRecords in RubyOnRails.

Techno-thriller and change management

The oath is broken. I wanted to add a new entry in this blog at least every 15 days, and failed miserably for one month.

Let's compensate that with 2 light subjects in one entry.

What if we were trapped in the energy shortage?

Michael Crichton has just released (at least in France) a new book where some eco-warriors are triggering massive natural catastrophies in order to make the world join their cause. I don't feel very inclined to what appear to be M. Crichton views on the climate (from what I know), however there is an issue I have been thinking of, that would be interesting to be written as a novel,... or maybe to be taken more seriously!

In 2 or 3 or 4 decades, we'll be short of petrol. In 60 years or so, we'll be short of gas. Uranium won't last much longer.

Ok, let's develop new technologies, new energies,... But how do we do science, research, technology? With computers, labs, cyclotrons,... All of these are pretty much energy intensive (and water, but that's another debate). What if 60 or 80 years were not enough time to find any viable solution to the energy crisis? Our scientists would be back to wood and stones to find the new super energy of the future? But how could they do that in a world that would certainly be a complete mess? You got it.

This could be interesting as a novel, but I would personnally prefer having a public announcement in the next 10 years saying that a major breakthrough has occurred in cold fusion,... Otherwise, how the hell would I be computing until my fingers are crippled? I really plan on living 60 more years!

You can't change the world alone

I am currently learning an interesting lesson. Since my arrival in my current company, I have introduced several practises, either for development or for management:

• TDD
• pair-programming
• features driven iterations
• more participation from the group to development decisions (let people decide what they want to do, as long as what need to be done is done)

So far, there have been some successes and some areas could really be improved. For instance, our java team had a moderate consciousness of the absolute need of a permanent green light for unit tests:

• we had in one month 426 builds (99 OK / 327 KO). Maximum OK in a row = 12, maximum KO builds in a row = 126

• the whole "unit" test suite takes 1 hour to run (for 1800 tests)

Those 2 examples are clear signs that true TDD is not practised around here. Among the many causes of that, I would register my lack of success at making people change their practises.

The white knight

We recently hired one of the best developers I ever met, in order that he could take some, if not all, my activities as a tech project leader. I had a second objective in hiring him. I knew that he would be good at reinforcing the messages that I had been somehow unsucessful to convey. He was my white knight,...

I really needed him: 2 is better than one, and a newcomer, with a different background is even better. We know software development from different shops. This guy and me are much stronger at convincing -together- that there are good practises that should become mandatory.

And we feel that this is not enough. The "planning game" can also be improved. So we are hiring a "agile consultant" to help us start the new release the right way. One of my personal objectives for this year is to get a perfect consistency of our roadmap, our iterations and our day-to-day development. This is a difficult task. So we need our "white knight",...

Feel it with your guts

Having a white knight is great to trigger change. It can give legitimity to your ideas, better ways of introducing them. But if you want good development practises to survive your presence (something I have been missing this past months), you need to make people feel them with their guts. They should suffer from atrocious aches in their stomach, each time they develop a piece of code without any test for it for instance.

How would you do that? We plan to introduce Dôjô (now I know why there are '^' on the 'o' thanks to my japonese lessons,...) to make people practise TDD the extreme way. If the drug is good enough, they should be hooked on forever.

[ah, good to be back at work after a really pleasant vacation week ;-)]

The hard piece - solved

What can I do as a kata tonight? Oh yes, the unsolved problem from this week's Dojo, of course!

Well, it was not unsolvable at all, you just have to cool down and try to write down things progressively.

The solution

The idea I had that evening is that, finding the position of the upper left corner of the ith subgrid in a grid, should be as difficult as finding the position of the ith square in a grid. Make as if the big grid is a small one with subgrids in each square.

So here are the formulas (perhaps it is clearer than my previous "explaining" phrase?):

# returns a square position (x, y) for the upper left corner
# of the "grid_nb"th subgrid in a grid
def get_subgrid grid_nb
square = Grid.new(@width / @sub_width, @height / @sub_height).get_square grid_nb
x = 1 + @sub_width*(square.x_pos - 1)
y = 1 + @sub_height*(square.y_pos - 1)
end

and

# returns a square position (x, y) for the "square_nb"th square in a grid
def get_square square_nb
x = 1 + (square_nb - 1)% @width
y = 1 + (square_nb - 1)/ @width
Square.new x, y
end

OK, and for the crazy ones, the formula that precisely calculates the position of the upper left corner of the "grid_nb" subgrid in a (w * w) grid with (subw*subh) subgrids (for instance, you can have a 6x6 grid with 6 2x3 subgrids):

1 + subw*((1 + (grid_nb - 1)% ((w / subw)) - 1) + w * (1 + subh*((1 + (grid_nb - 1)/ w) - 1))

No wonder why we couldn't get it rigth at once! Indeed, it took me slightly more than one hour to do that with 5 tests and 31 assertions in Ruby.

TDD as an unconscious habit

Thinking about the discussion I had about TDD after the Dojo, I feel that TDD should really become an unconscious skill. You have to train yourself consciously then to master it without thinking about it. You know the classical circle for learning:

1. Something I don't know I don't know - unconscious lack of skill
   
2. Something I know I don't know - conscious lack of skill
   
3. Somethind I know I know - conscious knowledge
   
4. Something I don't know I know - unconscious knowledge

Regarding TDD, the specific thing that should become inconscious is the exact rythm of what you are doing:

• either defining test cases - green bar
  
• either implementing test cases - green bar
  
• either implementing code to pass the test cases - red bar
• either refactoring code - green bar
• either refactoring test cases - green bar

Practising the Dojo with an attentive animator or practising pair programming with a merciless mate is a great way to get the habit.

Back from the Dojo

Gureto!! (Great in japanese)

The Dojo we had last evening was very instructive

The place

We were 11 people from various background sit around a computer and a keyboard with a videoprojector.

The master and the rules

The overall evening was really well mastered by the MC. He told us the rules:

• a recap from last Dojo session
  
• a brainstorming for the subject
• a vote
• several "randories" of 5 min each
• pair-programming. The co-pilot becomes the programmer when the randori is over and a new person becomes co-pilot
• TDD is mandatory and should be followed by the rule
• watchers are only allowed to participate to ask for explanations or to state that the current development is out-of context
• no more than 2 hours in a row (1 and a half is common)
• the aim is not to be productive but to learn as much as possible

The session

First of all, we had the choice of the language: either Java or Python (my coworker is also proficient in Prolog, but she was the only one). I voted for Python because first I wanted to taste another dynamic language such as Ruby, but also because I feel this kind of language is pretty well adapted to the Katas.

The Kata

The kata we chose is an idea I proposed from Cédric Beust blog: solve a Suduku grid.

First of all we started from a list of tests that we wanted to pass. And we lowered our ambitions from that point on,... So we started with a kid's suduku of 4x4.

And we had a first objective that was to find the solution when only one square was uncomplete.

All in all, something like 16 unit tests were implemented and everything went with a smooth pace. Until the hard part!

The hard part

When you learn martial arts, there are times when you feel at ease with the movements and there are times when something seems unnatural, uneasy. Then you have to struggle with yourself to feel the right way to do it. Ok, enough for the metaphor.

Everybody in the room stumbled on one algorithm that we could not get straight. Even with such brilliant minds around the table. We wanted to implement a function that would return the uppermost left corner of the ith subgrid of the suduku.

This may sound easy for a 4x4 grid but, I don't know why, we had the madness to try to solve it for the general case:

• a suduku of NxN
• with subgrids of WxH

We fiddled with /, % +1, x W,... but nobody could either code it or explain the right algorithm to others in the room.

I was myself pretty much disappointed as I was too tired to get it right and I felt there was a really smart solution to the problem (something like a fractal approach).

So I think this will be the subject of an upcoming kata and I will post the solution if available.

Cooling down

Eating a delicious home-made tiramisu, we exchanged on this experience. I had great pleasure exercising TDD with an integrist as MC (I will certainly blog later about that. For instance, why would you need to execute the tests when you have just written a test with a missing method? You know that it will fail!).

I think this kind of session is the real way of learning the practise to a group of programmers.

We also had a discussion around the Cascade style for development thanks to Laurent Bossavit (the MC) that told us a funny thing:

• the man that drawed the first cascade-style process for development, Winstom Royce, wrote, in the same article (« Managing the Development of Large Software »), that this style was "risky and invites failure".
  

This article was an inspiration for the great "V cycle", that spread so widely afterwards,...

Roman code kata: MCMLXXIV => 1974

I want to share a small code kata I did tonight.

The kata

Transform a roman number "MCMLXXIV" into a decimal number: 1974. This kata is extracted from the XP french website (here).


What! Ruby is not perfect ?!

Another example of DiD,... In my implementation, I wanted to get access to all the characters of a string: "CIV" to ["C", "I", "V"].

So I grab the ruby doc and after a few searches on the web, I realize that no nice method such as String#chars or String#each allows to get the characters in an array (here's a ticket for that issue).

I had to resolve to my_string.split(//) which is not quite natural and expressive.

TDD of course

I used TDD to progress with my development:

assert_equal(1, r_to_i("I"))
then
assert_equal(2, r_to_i("II"))
...

and I was quite glad to get the right code fast enough. Ok, agreed, it is not rocket science. But small successes make a happy day.

Lessons learned

The interesting thing about code kata is the time to consider what has been done and how it has been done. Specifically I wondered about the possible use of an injecter to reduce the code (which was a question on the web site):

def r_to_i r
result = last = 0
r.reverse!.split(//).each{|n|
T[n] >= last ? result += T[n] : result -= T[n]
last = T[n]
}
result
end

[funny thing : copying-and-pasting the code on the blog, I found several ways to reduce the code size. However, I feel a comment is necessary on the algorithm. I may not be understandable at first sight,...]

But I don't how it is possible since injectors are repeatedly cumulating the same operation on elements of a collection. Anyway, it was a good pretext to re-read the paragraph on the subject in ProgrammingRuby.

Ok, back to hiraganas now (I am currently learning japanese,...)

DiD : Devil in the Details,...

A new acronym, that can be encountered in so many workplaces, even literally speaking sometimes ! (Bwah, ah, ah, ah,...)

Time for a follow-up. I was pretty satisfied with my idea of implementing associations as first-class objects in our object-model. It truly serves its purpose : a fine management of relationships between objects: deletion, updating, adding,...

However, I would like to summarize also all the difficulties we had along the way, that's not always paved with flowers:

Transient/Persistent objects

We have some objects that are build only for the purpose of the application session. Those objects are displayed to the user but not meant to be persisted. Yeah, right. But hey, anytime you are associated with a business object, an underlying Observer-Observable relationship is build. It's fine until the business object is persisted and JDO kindly does "persistence by reachability" to persist anything connected. Bang! A transient object is persisted,...

Modification impacts outside the aggregate

With our framework, each time the marketing adds a new ProductRelease to the Product, the Catalog can be notified. All this stays in the same hierarchy of objects. But what if a corresponding new ManufacturedItem should be created in the Factory ?

Loosing my memory

Objects are cool, objects are fine and RAM is cheap,... but not infinite! Adding new objects to manage the relationships also adds more data and we had surprises with our memory consumption.

Redundant associations

Every relationship is managed as an association, even for redundant associations, that are only there for design reasons. As we also use our framework, in a very generic way, to create configuration files, we had never-ending instability each time a new association was added even if the business did not evolve.

Caches

A variant of the previous one. How should a cache of objects be managed? As a composition between the object owning the cache and the cached objects? Can the cached objects appear in compositions even if they are indeed shared?


Tackling the issues one by one

Ah the details,... They can truly turn any "brilliant idea" into "useless crap". Our current answers to those issues are:

• Transient/persistent: no obvious solution. Delete the objects when not used. Persist them temporarily if necessary. We are waiting for our supplier to implement JDO2.0 to implement an elegant solution.
  

• Modifications outside the aggregate: use the ubiquitous EventBus
  

• Loosing my memory: some attributes were unecessary on the associations. This had a nice impact. However since we don't have any way in Java to know who's using a specific object, we need to add extra-pointers
  

• Redundant associations / caches: this is a real case of "don't mess the business model with the design model". We redesigned our associations with more meaningful data. Is it a design association? Is the component object cached? And so on.

So far, so good, we didn't find a vicious little problem that could bring our framework down,... yet!

One more word: I wish we did all that in Ruby! Take a look at the ActiveRecords framework:

class Firm < ActiveRecord::Base
  has_many   :clients
  has_one    :account
  belongs_to :conglomorate
end

or

class Account < ActiveRecord::Base
  composed_of :balance, :class_name => "Money",
              :mapping => %w(balance amount)
  composed_of :address,
              :mapping => [%w(address_street street), %w(address_city city)]
end

It seems so clean :-O

Have you done your code kata today?

Scheme, ADA, Prolog,...

As I was reading Joel Spolsky's last post and the following discussion, I was reminded of my own education where I had to learn Scheme. So many parenthesis,...

I had a go at the test sample that Joel was referring to. It wasn't hard at all. But I realized why. At school, we were given so many exercises of money change management that anything like the sum of squares is a breeze:

• can you write in Scheme an algorithm that gives the change for a given amount of money having w 1 cent coins, x 2 cents coins, y 5 cents coins, z 10 cents coins?
  

Yes, I remember blowing one or 2 neurons off!

What's left from that? Frankly, I don't know. I certainly don't exercize this kind of ability each day. However I think it gives me a kind of mental agility that's fine to use when needed.

The other languages we were taught were SQL, Prolog and ADA. ADA mostly. With ADA, the emphasis was on implementation hiding, abstraction, data types. Basically the survival kit for doing some kind of design.

Give me OO, but keep me down on earth!

The other language that we should have learned was Smalltalk. No object-orientation in 1992?! Luckily, I had to cope with an object library for geometry in C++ as my first internship.

My first big project was also in C++, then I jumped on the Java bandwagon. What a relief, no more pointers/memory management! I could at last focus on object analysis, design patterns and so forth. Too easy my friend,...

The law of leaky abstractions strikes again. As an object zealot, I like to live in a world where everything is an object. Yet this is not the real world! I also live in a world where I have to manage memory for any non-trivial system.

I learned it the hard way,... My first financial system was full of small objects representing financial parameters. The server RAM was full of them too! Here come lazy loading strategies, careful collections selection and garbage collecting. Why wasn't I taught all these? Superficial teaching? Maybe the reason is that teachers don't have to learn it the hard way,...

The bottom line is that learning Java in CS courses is certainly ok, even if it presents a limited approach to programming. It is ok if you also learn the subtleties of java, not to be an expert, but at least not to fool yourself.

Learning Ruby

I specially liked Joel's post since I started learning Ruby this month. First of all the syntax, then the API (no more code completion!), then what?

I remembered an idea from the pragmatic programmer's book (I think): code katas.

Code katas are small programming/designing exercises. Each of them aims at developping a specific ability that useful in programming:

• Business analysis
• Data munging
• Data sorting
  
• Estimating size or speed
• ...

I would certainly add other katas to Dave's list:

• Threads management
• GUI building
• Memory management
• Network communication
• ...

The nice thing about katas is that they are written in a way that you have to think about how you solved the kata and what did you learned from that. High education is not the end of it at all. We have to much to learn to grasp software, from technique to business. And we have so much to learn about how we learn (take a look at the Dreyfus model for instance)!

Again, martial arts as a metaphor for programming is pretty interesting:

-Sensei, I practised my code katas today
-Well, well, Eric-san, the spirit of software will flow through you. Now, wax-in, wax-out!

What the market wants

I have been following a training session on the marketing of innovation. What a treat! Many times, the speaker told us: "if you should only remember one thing from this training, it is,..." which was a funny running gag (until he said "..., hum, not this one").

The market opportunity

Among the things to remember were:

• where's the need? is it conscious/expressed, comfort/strategic, adressed/covered?
• are you relevant -and- credible to cover it?
  

If there's a real need:

• conscious -> if possible (otherwise, it will be really hard unless you're a big corp)
• strategic -> necessarily (somebody has to start living again thanks to you)
• adressed -> always (don't dream awake, the world is not waiting for you to turn),
  

and you have something relevant enough to convince other people,...

then go ahead! You have a market.

Those 3 questions were so appealing that I couldn't help but think: "ok what would be the next need that I could fulfill with a new innovative product?" (unfortunately, I found nothing yet,... but asking the question again and again should bring something!)

Stay focused and prioritize

The rest is only one thing: stay focused. It is not so original (see Geoffrey Moore book) but this is the real trick to succeeding.

Product development, commercial development, communication development -are- terribly expensive and error-prone activities. So gather all your energies on the right battlefield.

Oh, yes, one more thing (hence the running gag,...): define a strategy that will allow you to extend your playground, once your primary, tightly-focused market is covered.

Write it down

On the way home, I applied all those principles to 2 prospective markets for our products. I found out something: it really pays to write down things when you do any strategic planning. I have often observed, in our board discussions, that the more recent customer event took the lead over any previous experience. This must have something to do with our limited brain capacities (see Herbert Simon "limited rationality" concept). By detailing numerous facts, I could determine many different reasons why one market was better than the other, and which kind of product and value proposition were to be made on each of them. I think that any discussion on the subject could have driven us into circles.

Just do it!

Innovative Entrepreneurship is not a piece of cake but it really looks like the world will never be quite the same when you succeed. Well, maybe even if you try!

Test-driven development : a practical guide - 2 years later

Oh well, this book (Test-driven development: a practical guide by Dave Astels) is not so new. Yet, I believe that not so many developers (including myself) have really acknowledged the messages it conveys.

Having read it 2 days ago, I take the opportunity to sum up some of the ideas that are exposed in this mind-agitating book.

1. Tests are only a by-product of test-driven development (TDD). The primary aim is to develop good software confidently (see my previous post on Behaviour-driven development)
   
2. Unit testing a java gui is possible
3. Developing a system with TDD leads to a well-crafted system if we refer to the metrics ran at the end of the sample project
4. Why would you ever need a debugger?

Now, more on my personal thought about this book and its messages:

Be humble

Dave insists (heavily,...) on that: do a tiny little bit at the time, and of course, as a real XPer, do the simple thing that could possibly work. I feel this is really not so easy. When I develop code, I am very, very, very tempted to write more than I have tests for. What in the hell could be wrong with that simple iteration on my collection to get the object with the right name?

The trouble is I have too often seen those kind of stupid mistakes:

int i = 0;
while (iterator.hasNext()){
t_object = (Entity) iterator.next();
if (t_object.getName().equals(p_name))
break;
}
return i;

OR

if (p_param >= 10);
doThat(p_param);

Yeah, it's so easy to write code, but it's so easy to write wrong code, even if you're more brillant than Marilyn vos Savant. By the way, did you spotted the errors? The first piece of code returned a counter that wasn't incremented,... and the second one had a supplementary semi-column after the decision in the if (I did this one at least 3 times in my coding career, and I am sick of it since my brain can be real slow on just spotting that parasite character).

So, be humble, don't trust your "best developer of the month" diploma, assume that every little bit has to be correct.

Use one set-up per fixture

This is a discovery for me. I always tended to think: "there should be at least a test class per production class". Yes, sure, but there can be so many more: the trick is to really use the setUp methods for factoring the fixtures for the assertions you want to make. And If you want to create another fixture, create an another class. This way you will end up with specific classes for specific contexts and with test methods that contain merely the minimum of what's needed.

There is no such thing as a free good design

From the beginning of his example, Dave shows us that he has a good idea of what should be a good design:

• proper use of interfaces
• clear separation between business code, UI code and persistence code
  
• ultra-thin UI (this allows an easier testing of the UI)

I think that TDD can reinforce a good design (hence the proper metrics at the end of the experiment) but I am not sure that TDD leads you automatically to a good design, even if you refactor a lot. This is why XP mandates the use of exploratory design. At some point you may have to experiment in order to find the right ideas.

Using the debugger is a "smell"

I read this months ago, and I often remember this when using the debugger. Using the debugger makes me think that I don't really know the behaviour of the system I am using. Then, like St-Thomas, I have to take a look at it.

Moreover the use of the debugger tends to encourage a code-and-fix attitude: I code, then I will ask the debugger for what is wrong. And this gets worse with tools such as Eclipse where you can modify code on the fly and re-execute it in the same debugging session.

So when you want to ascertain the behaviour of your system, it is much better to make an hypothesis and write a test case to make sure you're right.

Eventually, there may be a 5th XP value: Disciplin,...

Bouncing ideas

I had the great opportunity to participate in creativity and brainstorming trainings. When I first learned about brainstorming, we were taught the following rules:

1. say whatever you have in mind
2. the quantity is better than the quality
3. don't judge
4. you can copy on your fellows

This last rule is really interesting and was fairly reused in the creativity training I had 3 years ago (with a faboulous company: Synectics). It is the contrary of school (at least the french one)! Why not elaborate on other people ideas and catalyze new ones?

This why I feel great when I see that 2 of my recent blogs found an echo on the web. When I writed about the "attitude" of software testing, I wasn't aware that other people were already working on that matter, and they call that approach "Behaviour-driven development". This is not a revolution, just a different way of looking at the software we develop.

Similarly, I had heard a lot about Ruby on Rails and its ActiveRecord framework, but I just realized, reading Graham Glass's blog, that part of RoR popularity is certainly related to its support for associations and compositions. It really itches me to download Ruby and start using it. I wish I could have all these facilities of declaring properties such as "belongs_to" or "has_many" in Java.

So now, my only wish is that I have enough time to add my grain of salt to those developments,...