Monday, January 25, 2010

My TDD Struggle

I'm a huge fan of the concept of TDD (Test Driven Development).  I've done it a few times with varying success but I intend to make it a constant practice on anything new I write.  If you want to see people doing it right, go watch some videos at  Now on to the words!

TDD is the red/green/refactor process.  Write the test, watch it fail.  Go write the bare minimum of code possible to make it pass.  Refactor the code, and refactor the tests.  Repeat.

This process lends itself to what people call "emergent design."  This is the concept that you don't stress out trying to devise some all encompassing design before you begin coding.  You sit down, you write tests, and you let the design emerge from the process.  The reasoning here is that you'll end up with the simplest possible design that does exactly what you need and nothing more.

That point hits home very strongly for me because of my experience with both applications and code that have been over designed and end up causing all sorts of long term problems.  So the call for simplicity is one I am very eager to answer.

BUT.  Clearly you can't just close your eyes and code away and assume it will all work out.  There is an interesting tight rope walk happening here.  As you are coding you have to be constantly evaluating the design and refactoring to represent the solution in the simplest possible way.  But what TDD is really trying to get you to do is not think too much about what is coming next and instead pass the current test as though there wasn't going to be a next test.

It's that "ignoring" the future part that I really struggle with. The knee jerk negative reaction is that this will cost you time because you're constantly re-doing work.  There are times when this is probably true, but in general the tests lead you through the solution incrementally, affirming you're on the right track each step of the way.  And when you suddenly discover something that causes you to back track, you've got all the tests ready to back you up.

But there are a few things that I don't think this technique is good for.  One is "compact" algorithms, the other is large systems.  We'll take them one at a time.  I was recently practicing the Karate Chop Kata which is a binary search.  My testing process went like this:

  1. When array is null or empty it should return negative one
  2. When array has one item 
    1. it should return zero if item matches
    2. it should return negative one if item does not match
  3. When array has two items
    1. it should return zero if first item matches
    2. it should return one if second item matches
    3. it should return negative one if nothing matches
  4. When array has three items
    1. ...
Numbers 1-3 were all implemented in the straight forward way you would expect.  But when I get to #4, now I have to actually write the binary search algorithm.  So now I have to decide if I'm going to write it with a loop, with recursion, with some form of "slices", etc.  I also have to figure out what the terminating conditions are and verify that my indexes and increments are all correct.  In other words I have to do all the work after writing that one test.  

And worse, these tests are stupid.  What am I going to do, write a test for every array length and every matching index?  I re-factored the tests later to be a bit more generic and more specific to the edge cases of the algorithm in question.  If you'd like to see what I ended up with you can checkout the code on bitbucket.

In general, writing your tests with knowledge of the implementation you're writing is bad, bad, bad.  Like @mletterle reminded me of on twitter, tests should test the behavior of the code, not the implementation of the code.  Bob Martin just recently wrote a post that made the same kind of argument in regards to Mocks.  

Now don't get me wrong.  The tests are still valuable in this example, they're just not as useful in an "emergent design" kind of way.

Moving on, the second thing that the emergent design mindset isn't very good for is complex system design.  Systems that are complicated enough to warrant DDD (Domain Driven Design).  In this case you really want to step back and take a big picture view and do a real Domain Model.  The emergent design approach may lead to a design with fewer objects or something, but this may not be a good thing if you're interested in a design that excels at communication.

With these systems you'd do your Domain Driven Design, then drop into your TDD and allow it to "emergently" design the actual implementation code of your model.  You're kind of getting the best of both worlds this way.  But its important to recognize that TDD is still an important part of this, even though you didn't let it guide the ENTIRE design.

So TDD and emergent design might not be the answer in all circumstances.  But I still think that you'll find a strong place for it in even these circumstances.

Anybody in the blogosphere strongly disagree with this?  Or perhaps, dare I ask, agree?

Monday, January 11, 2010

SCM Trade-Offs

Source Control Management (SCM) is, on the surface, a very simple topic.  You put all your source code in one place, then you check in and check out from there.  Advanced systems support merging changes if two people edit the same file.  And there you go, SCM in a nut shell.

And if you are just one person, or a small team, that's probably where the story ends for you.  But with larger teams, or more complicated application environments SCM inevitably morphs into Application Lifecycle Management (ALM).  ALM covers topics from requirements, to architecture, to testing, and release management.

I have found that typically it is ALM requirements that end up introducing branching to your SCM.  Branching is another simple concept.  You make a copy of the source code which can later be "easily" merged back with the original.  Unfortunately branching is another area that quickly gets much more complicated than all that (which I've written about before, in a surprisingly humorous post if I may say so myself...).  As the number of branches increase the amount of work required to track them and merge between them increases.

So you will always find that there is a delicate trade-off that must be made when you introduce a branch.  Branches give you isolation, letting people work independently from each other.  There are tons of reasons why this can be helpful, some of which include:
  1. You can work without fear of breaking other people's work
  2. You can try "experimental" stuff which may never actually be finished
  3. You can work on parallel features and release one without releasing the others
  4. You can do new work while still enhancing an old release (ex: service pack releases)
But branches also introduce the need to integrate.  If everyone works on the same branch, every check in is an integration.  And these happen so frequently it's hard to even think of them as "integration."  But if you introduce long lived branches, integration can now be delayed indefinitely.  There are plenty of horror stories about companies which tried to delay integration to the very end of application development and then spent almost as long "integrating" as they spent "developing."

This is where Continuous Integration comes from.  The idea is that you want to integrate very often (at least once a day according to Fowler), and that you want integration to not just mean merging code, but also running tests to verify that the integration is successful.  The point is that you want to catch integration issues early.  The reasoning is the earlier you catch them the easier they will be to fix.  The longer you wait to fix them, the more things will have diverged, or be built on code that needs to change.  So integrate often.

And this is where we arrive at a problem I've been struggling with for quite some time.  On the one hand, I want isolation for all the reasons I've already mentioned.  And on the other hand I want to integrate continuously to avoid all the pitfalls mentioned.  But you can't have both.

Naturally I've tried to look at how other people tend to deal with this issue.  There seem to be two big picture approaches:
  1. "Centralized" in which everything starts integrated, and isolation must be purposefully added
  2. "Distributed" in which everything starts isolated, and integration is tightly controlled
All open source projects I've looked at are run very "distributed."  Anyone can download and update the code in their own sandbox.  But to actually get that code into the project you must submit patches, which the project leaders review and apply if they pass their standards.  This works well for Open Source projects because you can't let anybody waltz in and start changing your code.  You need control over what code is being added and modified, and you want it to all be reviewed and tested.

In contrast most company projects seem to be run "centralized."  Mostly I've found accounts of a main branch with release branches for past releases and maybe a few feature branches.  You can work code reviews into a process like this.  Some systems support preventing check ins without code reviews.  Other people just make it part of the "process."  But in general, people are trusted to be making the right changes in the right way, so the control required in OSS projects isn't as strictly needed here.  You trust your own employees.

I suppose I should mention quickly that my words "centralized" and "distributed" DO line up with the differences between Distributed and Centralized Source Control Systems (like Mercurial vs. Subversion), but you can still use a Centralized Source Control System and work in a "distributed" fashion by using patches.

There are lots of reasons why you might work one way or the other.  But I still have a hard time figuring out what's right for me.  This could be because my requirements are unusual.  I'm not sure why they would be, but I haven't found other people worrying about them.  This makes me think either my requirements are very special, or they're crazy and I'm missing something.

Briefly, here's what I'm dealing with.  I have a number of different people working on the same application, but they are all working on un-related or only loosely related features.  We have frequent and regular releases of the application being done.  We try to target features for the appropriate release, but its incredibly hard to know if a feature will really be "done" on time.  Features get pushed back when:
  1. They under go dramatic changes when it reaches completion and users try to put it through its paces
  2. The development takes longer than expected
  3. The developer gets pulled off and placed on another feature
  4. The feature gets put on hold for "business reasons"
If everyone is working on all this stuff in the "main" branch and integrating continuously, what do we do when one feature is not ready to release but the rest are?  The changes are all tangled up in the same branch now and there is no easy way to un-tangle them.

The only answer seems to be doing any "non-trivial" work in Feature Branches.

But feature branches pose whole challenges of their own!  If you're writing Mercurial, then feature branches are no problem.  If you're developing a website with a database then feature branches are a bit harder, because you have to create a new database and fill it with test data.  But if you're developing an enterprise application with a complicated database (which can't just be loaded with generated test data) that talks to other databases (with linked servers and service broker) and has a large number of supporting services many of which depend on OTHER 3rd party licensed services; then what?  In that case, creating the full application environment for each feature branch is actually impossible.  And creating a partial environment is certainly not easy.

But it is precisely because of all of this complexity that we want the isolation!  But the complexity makes the isolation difficult (if it's even possible, which I'm not sure of yet) and time consuming.  I love paradox!

Perhaps you're saying to yourself, "Maybe you wont be able to actually run the app and do everything it can do in your feature branch, but surely the code is written so all these things that depend on other things are nicely abstracted so that you WILL be able to run the unit tests!"  Um, no.  Sorry.  It pains me to admit it, but I'm afraid that isn't the case just yet.

So where does that leave me?  Well, I want to implement continuous integration to reduce the integration issues and make releasing easier, but I also want the flexibility to develop features independently so they don't prevent other features from being released, but my environment is so ridiculous that I can't figure out how to set it up so feature branches are fast and easy to create (and more importantly useful).

So, can you help me?  Do you have any of these problems?  Have you managed to mitigate any of these problems?  Am I missing something?

Saturday, January 9, 2010

Publish ClickOnce with Albacore and Rake

Rake is a great build system written on Ruby.  It uses the Ruby language to build a wonderfully simple Domain Specific Language (DSL) for writing build scripts.

If you look around a bit you'll find that people are using Rake for all kinds of things.  Even .NET projects use Rake, including Fluent NH and Machine.Specifications.

Albacore is a Ruby library for Rake which gives you a whole set of useful predefined tasks for doing common .NET tasks, like executing msbuild.

With Albacore, building a .NET solution is as simple as writing this rake script:
desc "Run a sample build using the MSBuildTask"
msbuildtask do |msb| = {:configuration => :Debug}
  msb.targets [:Clean, :Build]
  msb.solution = "spec/support/TestSolution/TestSolution.sln"
You execute that by simply typing "rake msbuild" at the command prompt.

You can even use Rake and Albacore to automatically perform a ClickOnce Publish!  For my office, I'm hoping that this will be a VERY useful thing.  To set it up, get the ClickOnce publish working in Visual Studio first.  With that done, write a rake script like this:
desc "Publish ClickOnce"
msbuildtask("publish") do |msb| = {
    "configuration" => "Release",
    "PublishDir" => "C:/temp/",
    "PublishUrl" => "C:/temp/",
    "InstallUrl" => "C:/temp/"
  msb.targets [:Publish]
  msb.solution = "slnFile.sln"

There are a few important things you have to get right for this to work.  First, you have to specify the PublishDir parameter or it wont copy your files to the PublishUrl.  Visual Studio makes this work automatically, but you have to do it manually if you want msbuild to do it.

The second thing to note is the use of forward slashes in the paths.  If you use backslashes you have to double escape them, once for Ruby, and once for cmd.  I have no idea why cmd needs the backslashes escaped, but that's the behavior I ran into and it's simpler to just use forward slashes.

With this all setup, you can run "rake publish" at the command line and your app will be ClickOnce deployed automatically.  You can also easily setup different ClickOnce deployments if you need to (ex: Test vs Production).

If you have any build steps at all that you think could be automated I highly recommend you check out Rake and Albacore.

Monday, January 4, 2010

Snow Blower Efficiency

Hi there, I'm a big nerd, and I'd like to prove it to you.

We've been getting a lot of snow in Cleveland, especially in the city where I live.  I use a snow blower to clear my drive way, and naturally I think about what the most efficient way to clear the drive way is while I'm out there in the cold doing it.

The solution I've come up with is somewhat interesting, so I figured I'd share.

There are a few factors to consider:
  1. Length of driveway
  2. Width of driveway
  3. Number of turns you make
  4. Number of turns of the thrower you make (the direction the snow is being thrown)
#1 and #2 are fixed, and there is nothing I can do (aside from buying a larger snow blower) to change those.  So the number of passes I have to make to clear the driveway is fixed.

Clearly, I'm going to go up and down the drive way, not side to side, as that will reduce the number of turns.  Given that, the number of turns I'm going to make is pretty much fixed.  Thus, the only other factor left for me to consider is the number of turns of the thrower I have to make.  As it "turns out" (har har), I actually can do something about this.  In fact, if I do it right, I shouldn't have to re-direct the thrower at all the entire time I'm clearing the drive way.

Here's two diagrams to help explain.  In the first diagram, I'm starting at the left top of the driveway and going up and down to the right.  In the second diagram, I'm starting in the middle and going down on the left and up on the right.

Notice that in the first image every time you turn, you have to also turn the thrower.  But in the second image the thrower is ALWAYS pointing to the right.  The downside to the pattern on the right is that your turns are wider, but I've actually found this is a good thing.  It's easier for me to make a wide turns than a sharp turn.

The last question is why start in the middle?  The reason is that when you're in the middle, the snow has to be thrown the farthest, and sometimes because of the wind or whatever it doesn't quite make it fully off the driveway.  By starting in the middle you make sure you never throw snow over ground you already cleared!

And with that, I have to go snow blow the driveway...  again.