J and I and Me
2012-04-01
  Testing Considered Harmful
Unit testing started with JUnit - and was infectious. As you can see in JUnit Test Infected: Programmers Love Writing Tests that was the intention from the very beginning. And so the infection spread.

Nowadays almost all programmers do extensive Unit Tests. And therefore we see problems arising. Instead of thinking about a problem and building a reliable solution developers now just write a test and code away. At one point they get a green bar and consider the job done. But can you build proper software that way? Dijkstra stated in 1972: "If you want more effective programmers, you will discover that they should not waste their time debugging, they should not introduce the bugs to start with." - see Wikiquote. I think the same holds true for testing. So instead of the ever famous code-test-refactor cycle we could use more of the Feynman Way of Solving Problems. If you really think about the solution first you will find you won't need a test. Instead you will actually write correct code from the beginning. You won't need to rely on tests. They cannot show the absence of bugs anyway - as Dijkstra mentioned. In the end you will end up with cleaner code and less code - as there are no tests to be written.

This principle can be applied to other areas as well. I think one reason why there are so many car accidents are the very effective brakes cars have now. If we had less effective brakes people would think about possible problems beforehand, drive more carefully - and we would have less accidents.

 
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Comments:
I'm not going to argue the main point of the article. At least not directly.

But I noticed that there are two wrong statements and one true that doesn't get elaborated enough.

1. Unit testing didn't start with JUnit. AFAIK JUnit was basically a migration of a Smalltalk tool.

2. By far not all programmers do write unit tests. If we are lucky maybe 50% write any relevant amount of unit tests. They just don't hang out on twitter and their blogs and brag about it.

3. Sure with bad brakes everybody would drive more carefully. But you can improve on that. Just make the ignition so bad that no car would start. Problem solved ... or maybe not.

Go figure
 
There are two very important cases for tests that even a correct code can not replace:

- Tests help refactoring when the requirements change .. and they will change

- Good tests show the requirements. In fact they are most times the only place where the requirements can be found
 
April Fools' Day?
 
April Fools' Day?
 
@Jens : In fact you are right, unit testing started in the Smalltalk community

@Sebastian: Absolutely correct!
 
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