Steve Freeman

We should be careful to get out of an experience only the wisdom that is in it—and stop there—lest we be like the cat that sits down on a hot stove-lid. She will never sit down on a hot stove-lid again, and that is well; but also she will never sit down on a cold one any more.

via Gemba Panta Rei

Twain also wrote of opera, “that sort of intense but incoherent noise which always so reminds me of the time the orphan asylum burned down.”

I don’t normally do this sort of thing, but this took my colleague Tony Lawrence and me a while to figure out and we didn’t find a good explanation on the web. This will be a very dull posting unless you need to fix this particular problem. Sorry about that.

We happen to be using the Spring database helper classes to talk to Oracle with stored procedures. It turns out that there’s a bug in the driver that means that you have to jump through a few hoops to pass values in when the input parameter type is a table. This should be equivalent to an array, but apparently it isn’t, so you have to set up the callable statement correctly. Where to do this was not obvious (to us) in the Spring framework.

Here’s an example stored procedure declaration:

CREATE TYPE VARCHARTAB IS TABLE OF VARCHAR2(255);

CREATE PACKAGE db_package {
  TYPE list_type IS TABLE OF VARCHAR2(50) INDEX BY BINARY_INTEGER;
PROCEDURE a_stored_procedure(
  table_in IN list_type
)

The table_in parameter type list_type is declared within a package, which means we can’t declare the parameter as an OracleTypes.ARRAY when setting up the statement. Instead we declare it as the type of the table contents OracleTypes.VARCHAR

class MyProcedure extends StoredProcedure {
  public MyProcedure(DataSource dataSource) {
    super(dataSource, "db_package.a_stored_procedure");
    declareParameter(new SqlParameter("table_in", 
                                      OracleTypes.VARCHAR));
    compile();
  }
  
  void call(String... values) {
    execute(withParameters(values));
  }

Here’s the money quote. When setting up the parameter, you need to provide it with a SqlTypeValue. Don’t use one of the helper base classes that come out of the box, but create an implementation directly. That gives you access to the statement, which you can cast and set appropriately.

   private Map<String, Object> withParameters(String... values) {
      return ImmutableMap.of("table_in",
                             oracleIndexTableWith(50, values));
   }

   private  <T> SqlTypeValue 
   oracleIndexTableWith(final int elemMaxLen, final T... values) {
     return new SqlTypeValue() {
       @Override
       public void setTypeValue(
         PreparedStatement statement, int paramIndex, 
         int sqlType, String typeName) throws SQLException 
      {
         ((OracleCallableStatement)statement).setPlsqlIndexTable(
            paramIndex, values, values.length, values.length,  
            sqlType, elemMaxLen);
       }
     };
   }
}

That’s it. Happy copy and paste.

Brian’s been paying us the compliment of taking our book seriously and working through our extended example, translating it to Ruby.

He has a point of contention in that he’s doubtful about the value of our end-to-end tests. To be more precise, he’s doubtful about the value of our automated end-to-end tests, a view shared by J.B.Rainsberger, and Arlo Belshee and Jim Shore. That’s a pretty serious group. I think the answer, as always, is “it depends”.

There are real advantages to writing automated end-to-end tests. As Nat pointed out in an extended message to the mailing list for the book,

Most significantly to me, however, is the difference between “testing” end-to-end or through the GUI and “test-driving”. A lot of people who are evangelical about TDD for coding do not use end-to-end tests for driving design at the system scale. I have found that writing tests gives useful design feedback, no matter what the scale.

For example, during Arlo and Jim’s session, I was struck by how many of the “failure stories” described situations where the acceptance tests were actually doing their job: revealing problems (such as deployment difficulties) that needed to be fixed.

Automating an end-to-end test helps me think more carefully about what exactly I care about in the next feature. Automating tests for many features encourages me to work out a language to describe them, which clarifies how I describe the system and makes new features easier to test.

And then there’s scale. Pretty much anything will work for a small system (although Alan Shalloway has a story about how even a quick demonstrator project can get out of hand). For larger systems, things get complicated, people come and go, and the team isn’t quite as confident as it needs to be about where things are connected. Perhaps these are symptoms of weaknesses in the team culture, but it seems wasteful to me to take the design experience we gained while writing the features not encode it somewhere.

Of course this comes at a price. Effective end-to-end tests take skill, experience, and (most important) commitment. Not every system I’ve seen has been programmed by people who are as rigorous as Nat about making the test code expressive or allowing testing to drive the design. Worse, a large collection of badly written end-to-end tests (a pattern I’ve seen a few times) is a huge drag on development. Is that price worth paying? It (ahem) depends, and part of the skill is in finding the right places to test.

So, let me turn Brian’s final question around. What would it take to make automated end-to-end tests less scary?

There are still a few places left for the London XpDay, an event designed by practitioners for practitioners.

We’re trying the half-Open Space format again, with a day of prepared sessions (some promising experience reports this year) leading to a day of ad-hoc sessions. This means we can have a conference that’s more responsive to the needs of the attendees in the room—if I want to cover a topic I can propose a session.

And we have some interesting keynotes. Apart from Mark Striebeck, talking about scaling up some agile techniques as only Google can, we’re continuing our tradition of bringing in ”outside“ speakers to trigger discussion. We have Doron Swade (who built the calculating engine in the Science Museum) talking about Babbage, and storyteller Terry Saunders.

Nat and I will also be using the opportunity to launch our book in the UK.

Prove you’re not superstitious! I’ll be giving my talk on Sustainable TDD at Skills Matter on Friday, 13th November. Sign up here (if you dare).

This talk is about the qualities we look for in test code that keep the development “habitable.” We want to make sure the tests pull their weight by making them expressive, so that we can tell what’s important when we read them and when they fail, and by making sure they don’t become a maintenance drag themselves. We need to apply as much care and attention to the tests as we do to the production code, although the coding styles may differ. Difficulty in testing might imply that we need to change our test code, but often it’s a hint that our design ideas are wrong and that we ought to change the production code. In practice, these qualities are all related to and support each other. Test-driven development combines testing, specification, and design into one holistic activity.

I just ran it at the BBC and people seemed to like it.

If you miss this opportunity, you can always see it at QCon San Francisco.

I’m running a track at QCon in San Francisco on Friday 20th November. The topic is Technical Skills for Agile Development, and it’s about some of the technical essentials that Agile teams need to keep moving.

I’ll be presenting a session, based on material from our book, on how to live with your tests over the long term.

See you there?

This “Darwinian” post that TDD Is Not For the Weak says that not everyone can cope with TDD, it’s for “the Alpha, the strong, the experienced”. I don’t want to believe this, because I think that developers who can’t cope with any level of TDD shouldn’t be coding at all, so I won’t.

This claim has been made for every technical innovation I’ve seen so far (objects, event-driven programming, etc, etc). Sometimes it’s true, but most of the time it’s about what people are used to. Michael Feathers pointed out a while ago that the Ruby community is happily exploiting techniques such as meta-programming that were traditionally regarded as needing a safe pair of hands. What’s changed is that a generation has grown up with meta-programming and doesn’t regard it as problematic. Of course, there will be a degradation in understanding as an idea rolls out beyond its originators, but there’s still some value that gets through.

Sure there’s a role for people to help the generation that is struggling to pick up a new technique, but that doesn’t mean that TDD itself will always be beyond the range of mortal developers.

A Liberal is a Conservative Who Hasn’t Been Mugged

I discover that our book Growing Object-Oriented Software, Guided by Tests is already up with the file sharers. This is before Nat and I have even seen a printed copy. I don’t know whether to be flattered that someone thinks our effort is worth pinching or annoyed that the production process has not protected our interests.

If you’ve downloaded a copy, remember that it took us three years to write, which includes a great deal of lost income. The least you can do is tell the world how good it is so that maybe we sell a few more copies.

In this post, Tobias Mayer argues against doing Extreme Programming (XP). I have a lot of time for Tobias, but I think he’s wrong on this one. I don’t know who he’s been talking to, but some of this is “strawman” argument, and I’d be more likely to be convinced if Tobias had tried XP just the once. XP is not a universal solution, but it is one possible choice and we know how to make it work.

As an occasional XP advocate, I don’t “blame Scrum for the lack of good development practices in the software industry”, I blame the software industry. If we worked in an effective industry, we wouldn’t be having methodology wars because things would just work. Now this same industry is messing up Scrum too by just taking on its ceremonial aspects. On the other hand, to blame XP for blocking good practice is just bizarre.

XP is a tiny movement that attracted some attention. What XP (version 1) did achieve was to show that it is possible to break through the logjam of cautious procrastination that still cripples many development teams, but without resorting to hackery. It gave teams a reliable package of practices that just worked. Of course XP didn’t take over the world because it’s not suitable for everyone–not least because it requires a degree of focus and skill that is not appropriate for many teams. Kent Beck’s presentation of XP version 1 was extreme on purpose: it was designed to inspire us huddled masses, and to stretch the boundaries of what was considered possible in software development, to reframe the discussion.

I think Tobias has forgotten just how far we’ve come in the last decade. That we have a craft movement at all is because XP put the actual writing of code back into the centre of the discussion–just look at who’s involved, it’s the same people. He also forgets just how counter-intuitive many of the XP practices are, especially compared to the direction the industry was moving at the time.

Tobias writes that the good development practices were spreading slowly at the time, but I’d argue that without XP we’d still be waiting. Test-Driven Development is still not that widely accepted and even the original C3 team didn’t adopt it fully until Kent was writing his book. Refactoring had a small academic following, but it’s not very safe without the compensating practice of TDD. I suspect most teams still ban changing code unless it’s to change a feature. Pair programming is still a very hard sell and, again, works much better in the context of TDD. I’ve seen enough Scrum teams that have not found a coherent set of technical practices. To say that they just need to improve their Scrum implementation begs the question of how Scrum is adopted and the limits of self-organisation.

Some final nit-picks. There are two editions of the XP book, the second is more recent than 12 years and has a “softer” approach to the methodology. As for the relevancy of the practices, the C3 project worked in an environment (Smalltalk/Gemstone) that still outclasses what most of us use today. Much of the work in the XP community has been to try to recreate that flexibility in inadequate current technical environments. What’s really scary is how slowly this industry moves.

About a month ago, Michael Feathers wrote another post that cited Gordon Ramsey. That reminded me to follow up my earlier post with observations from a couple of episodes from UK series 4 that make the point (thanks Channel 4).

First up is a curry restaurant in Nottingham (which has no shortage of competition) opened by an ex-sales manager and glossed up to look like an ’80s night club. Being from sales, his view is that the customers gets what they ask for, so he’s offering design-your-own curries—whatever combination you want. The result is that the kitchen brigade (who are good) can’t cope with the variety and turn everything to mush. When Ramsey has them cook all hundred-odd dishes on the menu, the waiting staff can’t tell which is which.

The owner sees the process as simple order-taking. Offer the customers whatever they ask for, regardless of the effects on the demoralised staff and low quality. It turns out that the customers aren’t curry experts and don’t like what they’re getting, so the restaurant is losing money. Ramsey’s solution is to cut the menu back to something the brigade can do well, and to offer what the customers what they actually want.

Second up is a carvery outside London that’s been bought by Scott, an ex-IT consultant. It’s losing money so, in an attempt to fill the place, he’s offering two-for-ones at below cost price; the only people who put up with the dreadful food are pensioners. He’s hired a cheap brigade who can’t even cope with the grill idea that Ramsey proposes, and the kitchen is so decrepit that Ramsey has it condemned. Scott is discovering that reducing costs isn’t working and risks poisoning the clientele.

Scott seems most comfortable in the office behind a computer, presumably planning the work that everyone will do. He appears to be the only owner in any of the series that has no interest in food or customers—the value part of the equation. He has no idea if his people are competent or what constitutes good service.

Back-to-back, the episodes make a nice pair. To belabour the point, we can’t do good, valuable work when the process is one-sided: when requirements are forced through an organisation without thought for the consequences, or when work is driven from behind the scenes without enough attention to a paying customer.

It should be obvious, but we need reminding. Hands up if you work in one of these places.