Rspec - Uniqueness shouldamatcher failing

Question

I have an ActiveRecord table with a column called name. I need this field to be present and unique. So I have the following specs

it { should validate_presence_of(:name) }
it { should validate_uniqueness_of(:name) }

And the corresponding rule in the model is:

validates :name, presence: true, uniqueness: true

My factory contains the following:

FactoryBot.define do
  factory :model_name do
    sequence(:name) { |n| "Name #{n}" }

    after(:build) do |model|
      pack.rels << build(:relation)
    end
  end
end

The problem is that when I run the specs I get the following error.

Failure/Error: it { should validate_uniqueness_of(:name) }
     
     Shoulda::Matchers::ActiveRecord::ValidateUniquenessOfMatcher::ExistingRecordInvalid:
       validate_uniqueness_of works by matching a new record against an
       existing record. If there is no existing record, it will create one
    Mysql2::Error: Field 'name' doesn't have a default value: INSERT INTO `table_name`

What am I doing wrong?

Please add your test -- this looks like an issue with your set up — dbugger
– dbugger, Commented Dec 12, 2024 at 15:19
I added where exactly I got the error, in which test I mean. Also added the factory — mrateb
– mrateb, Commented Dec 15, 2024 at 12:48
Your factory seems wrong - it’s not setting the name value in the table. Hard to tell where you have an error since everything in your examples has generic names. — dbugger
– dbugger, Commented Dec 15, 2024 at 16:55
Did you set subject in your test? e.g. subject {FactoryBot.build(:model_name)}? — engineersmnky
– engineersmnky, Commented Dec 23, 2024 at 20:41
This looks to be a problem that could be fixed by adding a database migration to set a default value to null or empty on the db level. Post your schema and migrations for this model — Andrew F
– Andrew F, Commented Dec 23, 2024 at 21:02

lmtaq · Accepted Answer · 2025-01-07 22:46:52Z

1

The validate_uniqueness_of matcher behaves differently in comparison to other matches because it creates an instance for the model if one doesn't exist yet. There is a Caveat section on the documentation detailing the scenario described in your question.

To solve this, you want to create an object with pre-populated fields within the scope of your tests, so you have control over the attribute values used during the execution.

Since you're using FactoryBot, you could do the following:

RSpec.describe ModelName, type: :model do
  describe "validations" do
    subject { FactoryBot.build(:model_name) }
    it { should validate_presence_of(:name) }
    it { should validate_uniqueness_of(:name) }
  end
end

answered Jan 7 at 22:46

lmtaq

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1 Comment

mrateb Jan 13 at 12:02

Perfect. Thanks for pointing this out from the documentation

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