Is TDD worth it?

Tuesday, May 12, 2009 3 minute read Tags: Unit Testing
Hey, thanks for the interest in this post, but just letting you know that it is over 3 years old, so the content in here may not be accurate.

Today Alistair Denyes finally gave the presentation on Integration Testing which he's been saying he'd give for something like 12 months, so I thought it'd be a good idea to get around to doing this post which I've been putting off for quite a while.

First off I'll start by saying that this isn't about the concept of testing, I do think that testing (both Unit and Integration) is a good idea, it's Test Driven Development (TDD) which I have some problems with.

One of the goals when I started LINQ to Umbraco was to ensure that I had high test coverage and that I followed TDD.
Well that turned out to be not such a good idea. 

Maybe I'll start with some background of what TDD is, just to make sure that we're all on the same page.

TDD is the idea of writing a test, watching it fail and then implementing the code to make the test past.
You do this over and over again, writing more and more code each time until you have all the scenarios completed.

And this is where I found the problem, while writing LINQ to Umbraco I had some idea of what I was doing, but not a huge idea. A lot of the code was prototyping before becoming the real code which got committed to CodePlex.
Starting to see why I don't think TDD works?

When you're going on theories your tests are often wrong, which means you write a test to validate an assumption which then turns out to be the wrong, when then makes the test invalid.

Also something else that I found out was that when I would go to write my first test I would then realise that I had a lot of missing classes/ methods/ etc so I would have to write a bunch of boilerplate code before I can even have compilable assertions!

And then while trying to write the code which would validate my assertion I realised that unless I was to design myself into a corner I would have to write even more boilerplate code!

So now the half a dozen lines required to valid an assertion has become dozens of lines over multiple classes.

Maybe I'm doing it wrong?


But I did find some value to TDD, when trying to write a LINQ provider which uses IQueryable<T> there's not a while lot of documentation, this meant that I was going to need some way to work out how to understand Expression Trees work. Thanks to TDD I did manage to write tests which would then run and I could follow their stack trace to determine what code was actually being executed!
This is how I worked produced A LINQ observation, oddly there isn't anything else I've found that explains that.