Rails: callback to prevent deletion - ruby-on-rails

Question

I've got a before_destroy callback that looks like this:
class Component < ActiveRecord::Base
has_many :documents, through: :publications
def document_check
if documents.exists?
errors[:documents] << 'cannot exist'
return true
else
return false
end
end
The test looks like this:
describe '#document_check' do
let(:document) { create(:document) }
let(:component) { create(:component) }
context 'with documents' do
before do
document.components << component
end
specify { expect(component.errors).to include(:document, 'cannot exist') }
specify { expect(component.document_check).to eq true }
end
context 'without documents' do
before do
document.components = []
end
specify { expect(component.document_check).to eq false }
end
end
I want it to raise the error if a component is in a document, but I can't seem to be able to write it correctly. The second test passes, the first doesn't:
Diff:
## -1,2 +1,2 ##
-[:document, "cannot exist"]
+[]
What am I doing wrong?

Answer 1

How is document_check being invoked? If manually (as you're 2nd tests seem to suggest) then you also need to invoke it for the first specify.
That is:
specify { component.document_check; expect(component.errors).to include(:document, 'cannot exist') }
That's horrible syntax, but you need to invoke the method before you can check the errors on it.

Answer 2

Here's the callback:
def document_check
return unless documents.present?
errors.add(:article, 'in use cannot be deleted')
false
end
And here's the passing test for it.
describe '#document_check' do
let(:subject) { create(:component) }
let(:document) { create(:document) }
let(:count) { Component.size }
before do
document.components << subject
subject.send :document_check
end
context 'with documents raises error' do
specify do
expect(subject.errors[:article]).to be_present
end
end
context 'with documents raises correct error' do
specify do
expect(subject.errors[:article]).to include(
'in use cannot be deleted')
end
end
context 'with documents prevents deletion' do
specify do
expect { subject.destroy }.to_not change(Component, :count)
end
end
end
Took ages but it's worth it.