TDD and BDD

Rails
1

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

2

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.

–
Phlip

3

Hi
Thanks for your reply
Sijo