Strange Little Problem

I just created a simple model and started to write unit tests for it
(I've cleaned out extraneous stuff).

The migration is:

class CreateMembers < ActiveRecord::Migration
  def self.up
    create_table :members do |t|
      t.column :name, :string
      t.column :number, :string
    end
  end

  def self.down
    drop_table :members
  end
end

The model is:

class Member < ActiveRecord::Base
  validates_uniqueness_of :number
end

The testing fixture is:

numeric_only_member:
  id: 1
  name: John Smith
  number: 15171914
alpha_numeric_member:
  id: 2
  name: Joanne Jones
  number: wke1234

So if I write a little test case (yes I know hard coded values are
fragile):

require File.dirname(__FILE__) + '/../test_helper'
require 'member'

class ExampleTest < Test::Unit::TestCase
  fixtures :members

  def test_uniqueness_of_member
    dup_member = Member.new(:name => 'duplicate', :number =>
'15171914')

    assert !dup_member.save
    assert_equal 1, dup_member.errors.count
    assert_equal "has already been taken",
dup_member.errors.on(:number)
  end
end

Problem:

"assert_equal 1, dup_member.errors.count" will fail with:
test_uniqueness_of_member(SimpleTest) [test/unit/simple_test.rb:11]:
<1> expected but was <2>.

The following line would also fail with:
test_uniqueness_of_member(SimpleTest) [test/unit/simple_test.rb:12]:
<"has already been taken"> expected but was
<["has already been taken", "has already been taken"]>.

Solution:

If I remove " require 'member' " from the test case then everything
passes. I have no idea why. (Yes I'm a newbie, please don't laugh and
point). I'm digging through ActiveRecord, UnitTest, and Ruby docs and
source but haven't found an answer yet. Any ideas?

Thanks...qb

I just created a simple model and started to write unit tests for it
(I've cleaned out extraneous stuff).

The migration is:

class CreateMembers < ActiveRecord::Migration
  def self.up
    create_table :members do |t|
      t.column :name, :string
      t.column :number, :string
    end
  end

  def self.down
    drop_table :members
  end
end

The model is:

class Member < ActiveRecord::Base
  validates_uniqueness_of :number
end

The testing fixture is:

numeric_only_member:
  id: 1
  name: John Smith
  number: 15171914

You might need:
   number: "15171914"
So that YAML keeps this a string and not an integer. You're not using members(:numeric_only_member).number so it might not matter (the database should be a string regardless).

alpha_numeric_member:
  id: 2
  name: Joanne Jones
  number: wke1234

So if I write a little test case (yes I know hard coded values are
fragile):

require File.dirname(__FILE__) + '/../test_helper'
require 'member'

You shouldn't need this as Rails will auto-load it when Member is first used.

class ExampleTest < Test::Unit::TestCase
  fixtures :members

  def test_uniqueness_of_member
    dup_member = Member.new(:name => 'duplicate', :number =>
'15171914')

    assert !dup_member.save
    assert_equal 1, dup_member.errors.count
    assert_equal "has already been taken",
dup_member.errors.on(:number)
  end
end

Problem:

"assert_equal 1, dup_member.errors.count" will fail with:
test_uniqueness_of_member(SimpleTest) [test/unit/simple_test.rb:11]:
<1> expected but was <2>.

The following line would also fail with:
test_uniqueness_of_member(SimpleTest) [test/unit/simple_test.rb:12]:
<"has already been taken"> expected but was
<["has already been taken", "has already been taken"]>.

Solution:

If I remove " require 'member' " from the test case then everything
passes. I have no idea why. (Yes I'm a newbie, please don't laugh and
point). I'm digging through ActiveRecord, UnitTest, and Ruby docs and
source but haven't found an answer yet. Any ideas?

Thanks...qb

I *think* that Member has already been defined when your 'require "member"' is executed and since the idempotency of 'require' is based on the argument (i.e., require 'foo' and require './foo' will load foo.rb from the current directory twice), the explicit require re-opens the Member class and hits the validates_uniqueness_of a second time. In addition to removing your "require 'member'", I'd also suggest writing your test like this:

class ExampleTest < Test::Unit::TestCase
   fixtures :members

   def test_uniqueness_of_member
     dup_member = Member.new(:name => 'duplicate',
                             :number => members(:numeric_only_member).number)

     assert ! dup_member.valid?
     assert dup_member.errors[:number]
     assert_match /has already been taken/, dup_member.errors.on(:number)
   end
end

You want to know that the record isn't valid, there's no need to actually try to save it.
You should check that the field has an error message, rather than the total error count.
I tend to test for things like error message text with regexps that will allow some flexibility in the actual value. (e.g., "has already been taken. Please choose another and try again.")

However, all you're doing is testing that the validates_uniqueness_of works. Don't you think that the Rails team already does that? You could make a case for verifying that something like a custom format is behaving correctly or that you're using the :scope option as you expect, but unless you're just practicing and convincing yourself how things work, I'd not normally test the things that Rails does.

-Rob

Rob Biedenharn http://agileconsultingllc.com
Rob@AgileConsultingLLC.com

As Rob pointed out, it's being caused by your model file being loaded
twice, and thus the validates_uniqueness_of being run twice. You end
up getting two (identical) error messages.

The "second" load of your model file is actually coming from the
"fixtures" line, which ends up calling:

   require_dependency 'member'

In order for require_dependency to do it's magic, it has to turn your
file name into an absolute path. So you get the effect of:

   require 'member'
   require '/some/absolute/path/to/member.rb'

Ruby doesn't know that these are the same file, so it ends up loading
the file twice, thus doubling the validates declarations.

So, the short answer is: don't "require" your models in your test
cases (or use require_dependency).

Rob, is that *all* he's doing? The test is too elaborate, but a case
could be made that this is a regression test for the business rule
that "Member numbers must be unique".

It would protect him from coming along later and inadvertently
removing that validation rule.

I agree that we shouldn't be testing Rails itself.

Stu Halloway addressed this at erubycon in Columbus,OH this summer.

Blog: http://relevancellc.com/2007/7/17/posted-slides-how-not-to-test-validations
Slides: http://relevancellc.com/assets/2007/7/17/KeepingTestsDry.pdf

If you're interested in a test to alert you when/if a validation is removed accidentally, then you should be devising a test for *that* (presence) and letting Rails make sure that validates_*_of does the right thing.

-Rob

Rob Biedenharn http://agileconsultingllc.com
Rob@AgileConsultingLLC.com

Well, that sounds good in theory. But in those slides, slide 18 looks
great but the stuff on 19/20 is a mess!

Devising a test for the presence of validates_uniqueness_of (instead
of exercising it) is non-trivial. And I'm not sure that's somehow
"better" or "DRY'er" than just trying to create a duplicate and seeing
it fail.

I'm really not trying to test whether I have a validates_uniqueness_of
declaration, and I'm not trying to test whether
validates_uniqueness_of works in the abstract (the test doesn't prove
that anyway). Instead, I'm trying to test that my model doesn't allow
the number to be duplicated (regardless of the details of the
implementation).

IMHO, something like slide 17 is the correct approach, and not 18.

Cheers,
Bob