Wednesday, May 21, 2014

Working Effectively with Unit Tests

Unit Testing has moved from fringe to mainstream, which is a great thing. Unfortunately, as a side effect developers are creating mountains of unmaintainable tests. I've been fighting the maintenance battle pretty aggressively for years, and I've decided to write a book that captures what I believe is the most effective way to test.

From the Preface

Over a dozen years ago I read Refactoring for the first time; it immediately became my bible. While Refactoring isn’t about testing, it explicitly states: If you want to refactor, the essential precondition is having solid tests. At that time, if Refactoring deemed it necessary, I unquestionably complied. That was the beginning of my quest to create productive unit tests.

Throughout the 12+ years that followed reading Refactoring I made many mistakes, learned countless lessons, and developed a set of guidelines that I believe make unit testing a productive use of programmer time. This book provides a single place to examine those mistakes, pass on the lessons learned, and provide direction for those that want to test in a way that I’ve found to be the most productive.
The book does touch on some theory and definition, but the main purpose is to show you how to take tests that are causing you pain and turn them into tests that you're happy to work with.

For example, the book demonstrates how to go from...

looping test with many (built elsewhere) collaborators
.. to individual tests that expect literals, limit scope, explicitly define collaborators, and focus on readability
.. to fine-grained tests that focus on testing a single responsibility, are resistant to cascading failures, and provide no friction for those practicing ruthless Refactoring.
As of right now, you can read the first 2 chapters for free at

I'm currently ~25% done with the book, and it's available now for $14.99. My plan is to raise the price to $19.99 when I'm 50% done, and $24.99 when I'm 75% done. Leanpub offers my book with 100% Happiness Guarantee: Within 45 days of purchase you can get a 100% refund on any Leanpub purchase, in two clicks. Therefore, if you find the above or the free sample interesting, you might want to buy it now and save a few bucks.

Buy Now here:

Monday, May 19, 2014

Weighing in on Long Live Testing

DHH recently wrote a provocative piece that gave some views into how he does and doesn't test these days. While I don't think I agree with him completely, I applaud his willingness to speak out against TDD dogma. I've written publicly about not buying the pair-programming dogma, but I hadn't previously been brave enough to admit that I no longer TDD the vast majority of the time.

The truth is, I haven't been dogmatic about TDD in quite some time. Over 6 years ago I was on a ThoughtWorks project where I couldn't think of a single good reason to TDD the code I was working on. To be honest, there weren't really any reasons that motivated me to write tests at all. We were working on a fairly simple, internal application. They wanted software as fast as they could possibly get it, and didn't care if it crashed fairly often. We kept everything simple, manually tested new features through the UI, and kept our customer's very happy.

There were plenty of reasons that we could have written tests. Reasons that I expect people will want to yell at me right now. To me, that's actually the interesting, and missing part, of the latest debate on TDD. I don't see people asking: Why are we writing this test? Is TDD good or bad? That depends; TDD is just a tool, and often the individual is the determining factor when it comes to how effective a tool is. If we start asking "Why?", it's possible to see how TDD could be good for some people, and bad for DHH.

I've been quietly writing a book on Working Effectively with Unit Tests, and I'll have to admit that it was really, really hard not to jump into the conversation with some of the content I've recently written. Specifically, I think this paragraph from the Preface could go a long way to helping people understand an opposing argument.

Why Test?

The answer was easy for me: Refactoring told me to. Unfortunately, doing something strictly because someone or something told you to is possibly the worst approach you could take. The more time I invested in testing, the more I found myself returning to the question: Why am I writing this test?

There are many motivators for creating a test or several tests:
  • validating the system
    • immediate feedback that things work as expected
    • prevent future regressions
  • increase code-coverage
  • enable refactoring of legacy codebase
  • document the behavior of the system
  • your manager told you to
  • Test Driven Development
    • improved design
    • breaking a problem up into smaller pieces
    • defining the "simplest thing that could possibly work"
  • customer approval
  • ping pong pair-programming
Some of the above motivators are healthy in the right context, others are indicators of larger problems. Before writing any test, I would recommend deciding which of the above are motivating you to write a test. If you first understand why you're writing a test, you'll have a much better chance of writing a test that is maintainable and will make you more productive in the long run.

Once you start looking at tests while considering the motivator, you may find you have tests that aren't actually making you more productive. For example, you may have a test that increases code-coverage, but provides no other value. If your team requires 100% code-coverage, then the test provides value. However, if you team has abandoned the (in my opinion harmful) goal of 100% code-coverage, then you're in a position to perform my favorite refactoring: delete.
I don't actually know what motivates DHH to test, but if we assumed he cares about validating the system, preventing future regressions, and enabling refactoring (exclusively) then there truly is no reason to TDD. That doesn't mean you shouldn't; it just means, given what he values and how he works, TDD isn't valuable to him. Of course, conversely, if you value immediate feedback, problems in small pieces, and tests as clients that shape design, TDD is probably invaluable to you.

I find myself doing both. Different development activities often require different tools; i.e. Depending on what I'm doing, different motivators apply, and what tests I write change (hopefully) appropriately.

To be honest, if you look at your tests in the context of the motivators above, that's probably all you need to help you determine whether or not your tests are making you more or less effective. However, if you want more info on what I'm describing, you can pick up the earliest version of my upcoming book. (cheaply, with a full refund guarantee)