TDD and BDD

Hi
    Could anybody please tell me what these?BehaviouralDrivenDevelopment
and TestDrivenDevelopment ? what are their pros and cons? And which is
preferred by rails?

Thanks in advance
Sijo

Sijo Kg wrote:

    Could anybody please tell me what these?BehaviouralDrivenDevelopment
and TestDrivenDevelopment ? what are their pros and cons?

TDD means you never write new lines of code until you have a failing test case that expects the code to exist.

A test case follows the Assemble Activate Assert pattern.

    def test_case
      a = assemble()
      q = a.activate(41)
      assert{ q == 42 }
    end

All TestCases first Assemble the data resources they intend to use.

Then they Activate a target method. (Preferrably the one you name your real test case after!)

Then they Assert that some side-effect, from that method, is within tolerance.

You write one of those first, get it to fail for the correct reason, and only then write new production code to pass the test. Repeating this in tiny cycles helps you avoid endless debugging.

Behavior Driven Development is TDD reinvented to use a literate framework. By "literate" I mean you try to use the verbiage that your client uses when expressing your business rules as requirements and specifications. So the AAA pattern becomes:

   specify 'the assembled activator adds 1 to its input' do
     a = assemble()
     q = a.activate(41)
     q.should.equal 42
   end

After that grammatical transformation, most of the concepts are the same. When you BDD-first, and write failing specs before passing them with new code, you are essentially doing TDD.

> And which is

preferred by rails?

Either. All projects should have tests (or specs), but Rails makes them easier than some systems we could mention because Rails was invented using TDD. And BDD specs can use the same "mock objects" as the TDD to write the same kinds of tests.

BDD has a slight "con", compared to TDD, because you need tons of extra verbiage (.should, .should_not, etc.) to get anything done. The BDD system (such as test/spec) will provide them, but you must still use them, and they don't look very programmerly. BDD is for high-level tests.

TDD has a slight "con" over BDD, because you cannot easily nest test cases, so each one tests a variation of the other. BDD does that very well. TDD is for low-level tests.

Neither have any "con" over the alternative - Code And Fix. No project should ever not have unit tests, and I can think of a project that should not use test-first.

Hi
    Thanks for your reply
Sijo