[rspec-users] Is BDD with RSpec cheaper?

Ben Mabey ben at benmabey.com
Mon Jul 7 15:40:55 EDT 2008

yitzhakbg wrote:
> This might be a loaded question on this forum, but here goes:
> Just had a discussion with a prospective employer, a Ruby On Rails shop. His
> reaction to BDD development on every project was skeptical, saying something
> like: "It depends on the project". "Some jobs are so short that the extra
> time invested in developing tests doesn't justify the cost".
> He was insistent that writing tests costs more. After all, you write twice:
> first the tests, then the code (or the other way 'round).
> My question is: From hard, practical, cold real world experience, is that
> so? Is BDD development more expensive? Let me qualify that. One could
> answer, "no, since the tests save you pain and heartache down the line". The
> question is whether BDD coding with RSpec is more expensive in the
> implementation phase and how much truth there is in the statement that BDD
> isn't for every project, like quick knock ups for example?

Does TDD/BDD take longer that hacking something out?  I would say that 
it depends a lot on the project and the developer's experience in that 
domain, BDD, and doing BDD in that domain.  That said, it probably isn't 
an unfair generalization to say that quick short jobs can be hacked 
together faster without tests.  Prototyping, spikes, and exploring new 
technology are times when BDD would probably hinder you.  As you point 
out though you will be building up a technical debt by not having tests 
that will come back and bite you at sometime.  That is why I generally 
throw away any prototype code and start over with a blank slate that I 
can start doing BDD with along with my newly gained knowledge from the 

I have experiences where doing BDD has greatly sped up my development 
and has helped me in compartmentalizing a complex problem into smaller 
more manageable sub-problems.  For a "quick knock up" then I think it it 
good to ask how long this software is suppose to live, and whether or 
not the developers have enough discipline to start adding tests once it 
does become more complex.  If the answer to the latter question is no 
then forgoing tests in the beginning sounds like a recipe for disaster.  
I suppose another question is how important this piece of software is.  
If it is just for fun and you just want to see some results and could 
care less about maintenance down the line then manual testing is just fine.

One more thing... you said "The question is whether BDD coding with 
RSpec is more expensive in the implementation phase...".
BDD is not just the implementation phase but is also the design phase as 
well.  I could certainly throw together some systems faster without 
doing BDD and then manually test the system afterwards.  Would I have 
confidence in the system?  Yes.  In fact, I would have just as much 
confidence in the system as I would if I had a spec/test suite verifying 
the behavior.  However, if I had created that system with TDD/BDD from 
the start I would end up with a greater sense of confidence of the 
*design*.  Easily tested code tends to go hand in hand with good design, 
where hard to test code tends to carry some code smells resultant of a 
poor design.  Which is another danger in delaying creating an automated 
suite because you may end up with hard to test objects which will be in 
dire need of some refactoring.

I don't know if I really answered your question or if I just added to 
your confusion.  In the end BDD, just like any other practice, has its 
trade offs and should only be applied in the right situations.  I think 
the "right situations" will vary from developer to developer/team to 
team and there may not be one single rule for where the exact cutoff is.


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