How to start unit testing or TDD?

Question

I read a lot of posts that convinced me I should start writing unit test, I also started to use dependency injection (Unity) for the sake of easier mocking, but I\'m still n

Answer 1

I would take on TDD, test-first development, before mocks and dependency injection. To be sure, mocks can help you better isolate your units - and thus do better unit testing - but to my mind, mocking and DI are more advanced concepts that can interfere with the clarity of just writing your tests first.

Mocks, and DI, have their place; they're good tools to have in your toolbox. But they take some sophistication, a more advanced understanding, than the typical testing neophyte has. Writing your tests first, however, is exactly as simple as it sounds. So it's easier to take on, and it's powerful all by itself (without mocks and DI). You'll get earlier, easier wins by writing mock-free tests first, than by trying to begin with mocks, and TDD, and DI all at once.

Start with test-first; when you are very comfortable with it, and when your code is telling you you need mocks, then take on mocks.

Answer 2

Test driven development can be confusing for beginners, a lot of books that I read when I was learning TDD would teach you how to write Unit Tests for a Calculator class but there seems to be very less help for building real world apps, that are more data centric if I dare say. For me the breakthrough was when I understood what is Behaviour Driven Development or BDD and how to start doing testing from outside in. Now I can simply advice you to focus on your application behaviour and write unit tests to verify it. There is a lot of debate going on between TDD and BDD but I think that well written automated tests at every level add value and to write them we need to focus on behaviour.

Hadi Hariri has an excellent post here http://hadihariri.com/2012/04/11/what-bdd-has-taught-me/

I have also written some articles on the topic that I feel will help in understanding all the concepts related to TDD here

http://codecooked.com/introduction-to-unit-testing-and-test-driven-development/

http://codecooked.com/different-types-of-tests-and-which-ones-to-use/

Answer 3

If you haven't written unit tests before, then just pick some classes and begin to write your unit tests, and continue to work on developing more unit tests.

As you gain experience you can then begin to mock out the database for example, by using the Unity framework, but, I would suggest starting simply and gaining experience before making this leap.

Once you are comfortable with how to write unit tests, then you can try doing TDD.

Answer 4

Read Pragmatic Unit Testing in C# with NUnit. It has comprehensive information about starting writing testes and structuring the code to make it more unit testing friendly.

Answer 5

Steve Sanderson has a great writeup on TDD best practices.

http://feeds.codeville.net/~r/SteveCodeville/~3/DWmOM3O0M2s/

Also, there's a great set of tutorials for doing an ASP.net mvc project that discusses a lot TDD principles (if you don't mind learning ASP.net MVC along the way) http://www.asp.net/learn/mvc-videos/ Look for the "Storefront" series at the bottom of the page.

MOQ seems to be the hot mocking framework lately, you may want to look into that as well

In summary, try to write a test to validate something you'r trying to archive, then implement the code to make it work.

The pattern is known as Red - Green - Refactor. Also do your best to minimize dependencies so that your tests can focus on one component.

Personally, I use Visual Studio Unit Tests. I'm not a hardcore TDD developer, but what i like to do is this:

1. Create a new project and define a few of the fundamental classes based on the system design (that way I can at least get some intellisense)
2. create a unit tests project and start writing unit tests to satisfy the functionality i'm trying to implement.
3. Make them fail
4. Make them pass (implement)
5. Refactor
6. Repeat, try to make the test more stringent or create more tests until i feel its solid.

I also feel its very useful to add functionality onto an exiting code base. If you want to add some new feature, first create the unit test for what you want to add, step through the code to see what you have to change, then go through the TDD process.

Answer 6

If you are curious about unit testing the best way to learn it is try it. You will probably start writing integration tests at first, but that is fine. When they seem too difficult to maintain or too much work to write, read more about what kind of tests there are (unit, functional, integration) and try to learn the difference.

If you are interested in starting with TDD, Uncle Bob is a good source. Particalulary this.

More on unit testing

Ensure that you get consistent test results. Running the same test repeatedly should return the same results consistently.

The tests should not require configuration.

Testing order should not matter. This means partial test runs can work correctly. Also, if you keep this design philosophy in mind, it will likely aid in your test creation.

Remember that any testing is better than no testing. The difficulty can be found in writing good clean unit tests that promote ease of creation and maintenance. The more difficult the testing framework, the more opposition there will be to employing it. Testing is your friend.