Code Retreat in Wroclaw

October 21, 2010

Next weekend there’s a Code Retreat in Wroclaw: I’ll be there so If you want to cut some code together retreat with us =)

expected exception in tests

July 26, 2010

I have a feeling too many people get it wrong so let me stress:

@Test(expected = SomeException.class) // IS BAD FOR YOU

I do enjoy jUnit a lot, thanks guys for sharing! Yet, I don’t like @Test(expected) feature of jUnit. In my TDD classes I simply teach to avoid using it. I admit the feature can potentially make few tests cleaner. However, it tends to bring more trouble than value. Newbies too often misuse it which leads to poor quality tests. Therefore:

Rule 1: don’t use @Test(expected)

My colleague (cheers Bartek!) pursues Master at the Uni. They teach him testing. One day a lecturer was presenting some test code:

public void testSomething() {
  //line 1: throws NullPointerException
  //lines 2-30: some crappy test code

The test is useless. Due to some bug in the setup the test method breaks in line 1. Therefore most of the test code is not even executed. The expected exception does great job in hiding this issue; the test is green! Therefore:

Rule 2: If you violate Rule #1 then at least make the exception very specific. Example:

public void shouldBuyBread() {}

Even if you use specific exception then the test does not document exactly where the exception is thrown. Sometimes it may lead to subtle bugs. Therefore:

Rule 3: Don’t violate Rule #1 when the test method has multiple lines.

Instead you can simply write:

public void shouldBuyBread() throws Exception {

  try {
  } catch (BreadOutOfStockException e) {}

Above is my preferred way of documenting ‘exceptional’ behavior. There you go, it is The Ultimate Test Template for ‘exceptional’ behavior.

JUnit is getting better. New goodies for exception handling in tests arrive. @Rule ExpectedException better documents what action triggers the exception. Also, it nicely maps to //given //when //then style. The downside is that you need some extra code if you want to interrogate the exception, for example if you want assert if exception message contains a substring (api as of 07-2010). Nevertheless:

Rule 4: Favor @Rule ExpectedException over @Test(expected) when test method has multiple lines.

Rule 5: Keep an eye on new versions of your testing libraries.

If you are already at RI in TDD than consider my Rule #1 as a safety net. You’ll never know when a new junior team member joins. He may easily misuse the patterns he sees in the codebase. Javadoc for JUnit does not say how to safely use @Test(expected) (at the moment).

If you are learning testing don’t get too upset with my dogmatic rules. If only you write any tests then I am smiling already. You smile too, write tests and be happy. Soon you’ll get your RI rank in TDD.

Rule 6: Write tests & smile!

//given //when //then forever

December 7, 2009
public void shouldDoSomethingCool() throws Exception {


I like to call it the Ultimate Test Template. I’m so fond of those 3 little comments but surprisingly, I didn’t buy it at first. Micheal (it’s you, tapestry-maven-iPhone fan boy =), friend from ThoughtWorks showed me it a couple of years ago. Actually, he didn’t show it to me – I just overheard him coaching a young dev about it. That day I thought I didn’t need any hip comments because my tests were great anyway. It was foolish.

Don’t be a fool like me and start writing //given //when //then today. Life is too short for messing around – you want to get level 85 in software craftsmanship soon, right? Here’s the deal: use the template for 1 iteration and if you don’t like the results then I will give you your money back. Seriously, no matter what you think about it – buy it! BTW. If you need to document some ‘exceptional’ behavior in your test somewhere there is the template for tests with exceptions.

Lately, I’ve been selling //given //when //then quite relentlessly. I even try to sell it via Mockito api. (The link also shows how to install the template in Eclipse so don’t miss it!)

I tried to lobby for the Church of given-when-then in Krakow, Warsaw & Kiev. I heard rumors that Wroclaw develops a growing number of brothers and sisters in faith =)

I think I forgot to thank Dan North for given-when-then and Liz Keogh for the idea of BDD aliases in Mockito. There you go!

TDD unlimited

November 26, 2009

So I read a short rant that questions TDD (or unit testing – it’s hard to figure). Here’s my message:

If you want to learn your trade don’t get too excited about gurus that outsmarted the Universe and found cracks in TDD. There are way more IT celebrities that successfully practice TDD. They blog about, they teach and you know what? Their code kicks ass big time. So… Write loads of tests, try TDD, taste BDD. Learn it yourself and at some point you won’t be needing blogs to decide what side to take (Alliance or the Horde? =).

Now, if you already know your trade please try to influence others to write more tests and learn TDD. How much inspirational is this or that! Anyway, it’s just my humble request to the world. Of course, you can write whatever you want, dear influential blogger!

Mockito in Zurich

June 21, 2009

I will have a pleasure presenting Mockito at Jazoon in Zurich. My session is on Thursday – make sure you don’t miss it. During the session I’m going to show few slides and do live TDD with Mockito & other mocking frameworks. I’m going to use Infinitest. Guys, it’s huge. Brett Schuchert wrote about it, Bartek told me to try it several times. Finally I did and I must say I’m impressed. Infinitest is like transcending to a real TDD.

is debugger a modern translator?

May 19, 2009

Couple of days ago we interviewed a young adept of the craft. We let him code but he got stressed out a bit and wrote very complicated code. At some point he stopped understanding the code he wrote. So he started using debugger to figure out the meaning of the code. This is when debugger became sort of a modern electronic translator.

The thing is we probably don’t want to use debugger as a translator. We prefer to understand the code we write. Instead of debugging I usually recommend writing a small test that covers the logic in question. You can try this exercise next time you are about to launch the debugger.

Don’t get me wrong – debugger is a handy tool in every developer’s kit. It’s just the less you use it the better you are in producing high quality code. Actually, it’s probably other way around – when you get fluency with TDD/simple design you will soon discover how rarely you use debugger.

excuses for not doing dev testing

May 12, 2009

Yesterday I heart loads of excuses why the tests have not been written. I immedietaly remembered Misko Hevery‘s session at amazing geecon conference (be sure to attend next year!). Misko told a story about influencing developers to write more tests, testable code and TDD. I liked his slide where he collected all the excuses he heart from devs explaining why they haven’t written tests. Basically, Misko’s conclusion was that the only valid reason of not writing tests/TDD was lack of skill. TDD or ability to write tests is a skill like any other and it is no shame if you haven’t acquired it yet!

However, some of the excuses I heart yesterday were beyond any common sense:

  • this is not really worth testing
  • this is a small application
  • we don’t have time
  • (my favorite one) tests would make it harder to refactor

That was all bullshit and the only reason the tests were not written was that it was hard to write them. Devs didn’t know how to write tests for the DAO layer (how to ensure db is in correct state, how to maintain test database, etc.). Devs didn’t know how to write integration tests because of lack of experience with tools like Selenium. So they didn’t write any tests, not even plain jUnits.

Half a year ago, the same development team wrote loads of tests achieving high quality code base & high test coverage. Those days they wrote a django application. Django is a modern framework with built-in means of testing. It significantly contributed to the fact that developers wrote tests without cheating themselves with it’s-not-worth-testing kind of excuses (complete list above).

The interesting thing about the situation I encounter yesterday was this: junior developer wanted to write tests for some DAO code that did not have any tests (actually, there were zero tests at all…). So I asked senior developer responsible for architecture to help out setting up a TestCase that can prepare connection to test database, etc. Instead of helping, the senior guy started his mantra of excuses trying to convince junior developer not to write tests. Fortunately, I was there…