Can do unit test without TDD?

Question

I'm in a project where we don't do TDD, because our bosses and the cliente are very "old styled" people. Because I can't do design through TDD but I feel fear to changes, I would like to write unit tests for my own safety. But, how those unit test would be? Do I have to write a test for each method specification for test that they do what it's supposed they do? Do I have to test for each new functionality like TDD but without design? I have a mess in my mind.

Thanks in advance.

Answer 1

You probably can't hurt anything by doing unit tests - regardless of how well they're done - except for one possible side-effect, and that is false confidence.

We tend not to do hardcore TDD, nevertheless the unit test coverage ranges from non-existent to moderate depending on project, and is becoming increasingly valuable as the idea settles in.

For general pointers, I'd say the following are key priorities for you right now:

• Test what you know to be important
• Test what you know to be fragile
• Write tests to expose any new bugs, then solve the bug by making modifications that pass the test
• Apply TDD where possible to any new features
• Acknowledge that you can't TDD an existing project. By its nature, TDD only applies to new ground, whether that's a new product, or a new feature for a legacy product. Don't let this fact dishearten you.

Answer 2

Yes. TDD is yet another software development technique which happens to utilize unit testing heavily. Unit testing as a process is fine on its own without TDD behind. Not to mention, sometimes it's not even possible to do TDD yet you do write tests (think legacy systems/existing untested code testing).

But as for what you should test. Depending how deep with testing you want (can) go, you can start with end user oriented functionality, through system components testing (ie. class contracts) up to simply assuring your code does what you claim it does - that's pretty much the final, most fine-grained unit test which you'll most likely have a lot of.

In general, what to test is not an easy question, I've happened to answer several variants of that question already, to give you few tips:

• test what your code does, not what it does not
• if you got certain requirement, have a test covering it
• test single feature at time
• focus on public contract, skip private bits

Also, reading few of the top voted unit testing questions might give you some ideas on why you will benefit from testing, regardless of using TDD or not.

Answer 3

When you say "we don't do TDD", do you mean that others don't practise TDD or that your bosses forbid you from practising TDD? If it's the first one, then you can practise TDD as much as you want, as long as you don't try to force other people to do it. If it's the other one, then tell your bosses that they pay you to write code the best way you know how, and TDD is part of how you do that.

You can certainly write tests without practising TDD. People do it all the time. Use the old saying, "Test until fear turns to boredom". Write tests for whatever you fear might not work correctly.