Is #valid? automatically called?

Testing RSpec
1

Does RSpec automatically call #valid? on ActiveRecord models?

For instance, when this example is run:

it ‘should reject a nil value’ do
@form = TimeShiftForm.new :file => nil

puts “@form.errors.count = <<#{@form.errors.count}>>”
@form.should have(1).error_on :file
puts “@form.errors.count = <<#{@form.errors.count}>>”
end

This is printed:
@form.errors.count = <<0>>
@form.errors.count = <<1>>

However, I never called @form.valid? , which leads me to believe that
RSpec called it for me.

If RSpec does in fact call #valid? automatically, should we refrain
from manually calling #valid? ?
-Nick

2

On Thu, Feb 12, 2009 at 11:03 AM, Nick H. [email protected]
wrote:

end

This is printed:
@form.errors.count = <<0>>
@form.errors.count = <<1>>

However, I never called @form.valid? , which leads me to believe that RSpec
called it for me.

If RSpec does in fact call #valid? automatically, should we refrain from
manually calling #valid? ?

RSpec doesn’t call #valid? automatically in all cases…but if you
look at the source for error(s)_on in
spec/rails/extensions/active_record/base.rb you’ll see that it does
call #valid? automatically.

Pat

3

On Feb 12, 2009, at 1:03 PM, Nick H. [email protected] wrote:

Does RSpec automatically call #valid? on ActiveRecord models?

For instance, when this example is run:

it ‘should reject a nil value’ do
@form = TimeShiftForm.new :file => nil

puts “@form.errors.count = <<#{@form.errors.count}>>”
@form.should have(1).error_on :file

This matcher, have(1).error_on, does call #valid.

puts “@form.errors.count = <<#{@form.errors.count}>>”
end

This is printed:
@form.errors.count = <<0>>
@form.errors.count = <<1>>

However, I never called @form.valid? , which leads me to believe
that RSpec called it for me.

In this case, yes, because the matcher needs that.

If RSpec does in fact call #valid? automatically, should we refrain
from manually calling #valid?

The fact that you are asking this shows that we’re violating the
principle of least surprise. We could make it so it doesn’t validate,
but that would pit the onus on users to validate explicitly (not to
mention the upgrade burden).

Thoughts?

David

4

On Thu, Feb 12, 2009 at 11:59 AM, David C. [email protected]
wrote:

@form.should have(1).error_on :file

pit the onus on users to validate explicitly (not to mention the upgrade
burden).

Thoughts?

Yes it’s a surprise, but maybe a pleasant one? I actually didn’t know
about this until 2 weeks ago :slight_smile: One of my coworkers showed me a spec
that included error_on but didn’t explicitly call valid? We both
scratched our heads a bit, prompting me to check out the code.

I think it’ll catch a few people by surprise. I don’t know that it
will lead to errors though. And I think it keeps the code a bit
cleaner (valid? may be explicit, but it’s noisy as well), still
expressing the intent well.

Pat

5

It seems logical that #errors_on would call valid? Otherwise, how would
it know?

///ark

6

2009-02-12 15:42, Pat M.:

The fact that you are asking this shows that we’re violating the
principle of least surprise.

Yes it’s a surprise

How do you know #errors_on not implicitly validating wouldn’t be
bigger surprise? Say 30 (instead of three now surprised) people would
be surprised.

Would documenting implicit validation on code comments. Now it only
says “Extension for should have on AR Model instances” on #errors_on.
And imo it could very well say “Calls #valid? before returning list of
errors.” too, although seeing that yourself from source is only one
click away if you you have dug yourself that deep in rspec-rails rdoc.

7

Mark W. wrote:

It seems logical that #errors_on would call valid? Otherwise, how would it know?

That intuitively makes sense.

The reason the whole issue is confusing is because of AR’s behaviour:

User.new.valid?
=> false

User.new.errors.to_a
=> []

errors_on(:foo) looks like it’ll call errors.on(:foo), which returns nil
if valid? isn’t called.

Scott

8

2009-02-12 21:27, Mark W.:

It seems logical that #errors_on would call valid? Otherwise, how
would it know?

…and that’s exactly what I thought too.

9

On Thu, Feb 12, 2009 at 8:31 PM, Tero T. [email protected] wrote:

2009-02-12 15:42, Pat M.:

The fact that you are asking this shows that we’re violating the
principle of least surprise.

Yes it’s a surprise

How do you know #errors_on not implicitly validating wouldn’t be
bigger surprise? Say 30 (instead of three now surprised) people would
be surprised.

Well, I don’t know. If you’ve used Rails for a while you know that AR
objects don’t have errors attached to them until valid? is called.

Anyway, I think overall the implicit valid? is a good thing.

Pat

10

On 12/02/2009, at 2:59 PM, David C. wrote:

@form.should have(1).error_on :file

validate, but that would pit the onus on users to validate
explicitly (not to mention the upgrade burden).

Thoughts?

David

I think it comes down to how much work you expect to have to do
yourself, versus how much “magic” you expect will, or would like to,
happen in the background.

It never crossed my mind that a matcher would call #valid? . My
impression of matchers was that they simply reported on whether or not
an object had a specific setting/property. I figured the matcher
simply checked the AR model object for the specified error, regardless
of whether or not I’d called #valid? .

Personally, I don’t think that matchers should be modifying the
objects that they check. In my mind, a matcher is like an overseer: it
reads and reports, but doesn’t tinker.

Another reason that I think matchers shouldn’t call #valid? is because
of the inconsistencies doing so can produce between spec examples.
Examples that use have(X).errors_on won’t have an explicit call to
#valid? , while examples that don’t use that matcher, but need #valid?
to be called, will have an explicit called to #valid? .

That’s my perspective on the matter. However, I’m not necessarily
advocating that the current behaviour change. Others have said that
they find it logical that #valid? is called for them. Who’s to say
who’s right?
-Nick

11

On Feb 13, 2009, at 10:52 AM, Nick H. wrote:

@form.errors.count = <<0>>
The fact that you are asking this shows that we’re violating the
happen in the background.

Another reason that I think matchers shouldn’t call #valid? is
because of the inconsistencies doing so can produce between spec
examples. Examples that use have(X).errors_on won’t have an explicit
call to #valid? , while examples that don’t use that matcher, but
need #valid? to be called, will have an explicit called to #valid? .

That’s my perspective on the matter. However, I’m not necessarily
advocating that the current behaviour change. Others have said that
they find it logical that #valid? is called for them. Who’s to say
who’s right?

I must say that I found it a bit surprising when I started using rspec
with rails (back in 0.8 or something like that).

It’s something I figured out after a bit of head scratching, but I
think it’s something my specs are better for in the long run. If it
didn’t call valid?, I’d probably end up defining a helper method for
my specs that wrapped that behavior.

Scott