Trying out TDD, getting stuck!

nelson · January 19, 2009, 9:11pm

I’ve heard about TDD, read about TDD, and now I’m trying to practice it.
However, I’m getting stuck trying to do a simple test in rails 2.2.2.
I’ve decided to try writing a simple functional test to test the
‘add_item’ action of my cart controller.

However, I got as far as this before my test was already not running:

test “should add an item to the cart” do

end

My cart controller uses two ‘fake’ models (cart_session,
cart_session_line_item) that aren’t activerecords. however i’m getting
this error message:

ActiveRecord::StatementInvalid: SQLite3::SQLException: no such table:
cart_sessi
on_line_items: DELETE FROM “cart_session_line_items” WHERE 1=1

for the life of me, I don’t understand why my test would be hitting the
database yet when my test body is blank and why it thinks that
cart_session_line_item is an activerecord when it’s not wired up as
such.

i know TDD is a good thing, and any help would be greatly appreciated!

Thanks,
Nelson

nelson · January 19, 2009, 10:06pm

On Jan 19, 2:11 pm, Nelson H. [email protected]
wrote:

cart_session_line_item is an activerecord when it’s not wired up as
such.

Are you sure your models are not inheriting from ActiveRecord::Base?

Even if you’re not calling any methods on them yet, the sheer act of
deriving from ActiveRecord::Base will necessitate the presence of
those tables.

i know TDD is a good thing, and any help would be greatly appreciated!

Thanks,
Nelson

TDD is a good thing! Let’s see if we can’t get this working for you.

Jeff
purpleworkshops.com

nelson · January 19, 2009, 11:32pm

Nelson H. wrote:

Are you sure your models are not inheriting from ActiveRecord::Base?

Even if you’re not calling any methods on them yet, the sheer act of
deriving from ActiveRecord::Base will necessitate the presence of
those tables.

Thanks for the response! I just double checked the two models and
neither of them derive from ActiveRecord::Base.

Can you post the source to either class?
Also note that inheritance is not equal to derivation.

–
Roderick van Domburg
http://www.nedforce.com

nelson · January 19, 2009, 10:40pm

Jeff C. wrote:

Are you sure your models are not inheriting from ActiveRecord::Base?

Even if you’re not calling any methods on them yet, the sheer act of
deriving from ActiveRecord::Base will necessitate the presence of
those tables.

Thanks for the response! I just double checked the two models and
neither of them derive from ActiveRecord::Base.

nelson · January 20, 2009, 4:34am

Nelson H. wrote:

Thanks for the response! I just double checked the two models and
neither of them derive from ActiveRecord::Base.

Use ‘script/generate model my_model’ to generate models. They will come
complete
with empty unit tests, empty data fixtures, etc.

Then, learn TDD using the “unit” tests, meaning the tests on the models

not
the “functional” tests on the controllers!

Anything your users can do to data thru the view and controllers, your
unit
tests should be able to do to the model objects thru their public
methods.

Only after you are proficient at the “unit” tests should you try more
advanced
and indirect testing!

nelson · January 20, 2009, 1:12am

Roderick van Domburg wrote:

Can you post the source to either class?

cart_session.rb

class CartSession
attr :items
attr_accessor :building
attr_accessor :use_corporate_account
end

class CartSessionLineItem
attr_accessor :sku, :quantity, :sku_id

def initialize(sku_id, quantity)
@sku_id = sku_id
@sku = Sku.find(sku_id)
@quantity = quantity
end

def total
sku.skuable.price * quantity
end

end

Also note that inheritance is not equal to derivation.

OK, I have to admit, I feel dumb here. I always thought inheriting from
a class was deriving from it. Is my terminology all messed up?

nelson · January 20, 2009, 2:14pm

On Tuesday 20 January 2009 03:50 am, Roderick van Domburg wrote:

I take that back and you are right. Must have had my head up in the
clouds at that time of writing.

Maybe me too–I’ve been watching this thread waiting for a clue as to
what TDD is–my out of the blue guess is Top Down Design, but I’ll do
better to ask…?

Randy K.

I didn’t have time to write a short letter, so I created a video
instead.–with apologies to Cicero, et.al.

nelson · January 20, 2009, 2:20pm

Randy K. wrote:

On Tuesday 20 January 2009 03:50 am, Roderick van Domburg wrote:

I take that back and you are right. Must have had my head up in the
clouds at that time of writing.

Maybe me too–I’ve been watching this thread waiting for a clue as to
what TDD is–my out of the blue guess is Top Down Design, but I’ll do
better to ask…?

Randy K.

not a bad guess, but try Test Driven Design/Development.

HTH

Matt

nelson · January 20, 2009, 3:31pm

On Tuesday 20 January 2009 08:19 am, Matt H. wrote:

not a bad guess, but try Test Driven Design/Development.

Test-driven development - Wikipedia

HTH

Matt,

Yes, thank you!

Randy K.

I didn’t have time to write a short letter, so I created a video
instead.–with apologies to Cicero, et.al.

nelson · February 7, 2009, 2:37am

Well, I figured it out, so I’m going to update my thread and hopefully
help someone in the future.

The problem was in test_helper.rb on this line:

fixtures :all

Anyways, thanks for everyone’s responses. And thanks to Phlip’s
suggestion about starting out with unit tests. They were much easier to
start with, and now I feel more comfortable with tests.

Randy K. wrote:

On Tuesday 20 January 2009 08:19 am, Matt H. wrote:

not a bad guess, but try Test Driven Design/Development.

Test-driven development - Wikipedia

HTH

Matt,

Yes, thank you!

Randy K.

I didn’t have time to write a short letter, so I created a video
instead.–with apologies to Cicero, et.al.

nelson · January 20, 2009, 9:50am

Nelson H. wrote:

cart_session.rb

class CartSession
attr :items
attr_accessor :building
attr_accessor :use_corporate_account
end

class CartSessionLineItem
attr_accessor :sku, :quantity, :sku_id

def initialize(sku_id, quantity)
@sku_id = sku_id
@sku = Sku.find(sku_id)
@quantity = quantity
end

def total
sku.skuable.price * quantity
end

end

That looks right. Is there perhaps a fixture lingering around?

Also note that inheritance is not equal to derivation.

OK, I have to admit, I feel dumb here. I always thought inheriting from
a class was deriving from it. Is my terminology all messed up?

I take that back and you are right. Must have had my head up in the
clouds at that time of writing.

–
Roderick van Domburg
http://www.nedforce.com

nelson · February 7, 2009, 2:38am

Oops… I forgot the actual fix. The fix was to comment out:

fixtures :all