RSpec nested route - NoMethodError: undefined method `customer' - ruby-on-rails

Question

I am trying to test a nested route however I am getting a undefined method customer for nil:NilClass. I have got the following RSpec test:
let(:valid_attributes) do
{alert_type: 'Error', subject: 'Triple-buffered responsive system engine',
state: 'Allocated', run_date: '2013-09-30 13:56:58', priority: 1, examined_on: '2013-09-30 13:56:58'
}
end
let(:valid_card_attributes) do
{name_on_card: 'Botsford', expiration_date: '2013-09-24',
expiration_month: '2013-09-24', valid_year: '2013-09-24', valid_month: '2013-09-24',
card_number: '2456-6996-2785-3769', bin: '8384-0294'
}
end
let(:valid_violation_attributes) do
{internal_code: 'Subsche', rule_priority: '96',
rule_id: '10', account_id: '10',
authorisation_id: '356'
}
end
let(:valid_customer_attr) do
{ first_name: 'CustomerString', last_name: 'CustomerString',
address1: 'CustomerString' , address2: 'CustomerString', post_code: 'CustomerString',
telephone: 'CustomerString', country: 'CustomerString', member_id: 1,
merchant_id: 1
}
end
let(:valid_session) { {} }
context 'JSON' do
describe 'GET show' do
it "delivers an alert with ID in JSON when a user requests '/api/alerts/id'" do
alert = Alert.create! valid_attributes
get :show, {:id => alert.to_param}, :format => :json
assigns(:alert).should eq(alert)
end
end
describe 'GET customer'
it 'delivers an alert with a customer and associated card' do
alert = Alert.create! valid_attributes
customer = Customer.create! valid_customer_attr
card = Card.create! valid_card_attributes.merge(customer_id: customer.id)
Violation.create! valid_violation_attributes.merge(alert_id: alert.id, customer_id: customer.id)
get :customer, {:id => alert.to_param}, :format => :json
assigns(:alert).customer.cards.first.should eq(card)
end
end
end
The console.log of the error that I am getting back is:
NoMethodError: undefined method `customer' for nil:NilClass
./app/models/alert.rb:10:in `customer'
./app/controllers/alerts_controller.rb:22:in `customer'
./spec/controllers/alerts_controller_spec.rb:33:in `block (3 levels) in <top (required)>'
Doing violation.first.customer just simply returns the first violation and the associated customer.
Be interested if anyone can shed any light on this.

Answer 1

violations.first in your Alert class is nil.
You're not setting up any Violations for your Alert in your test, so #alert.violations will be an empty array. Calling first on an empty array is nil, and you can't call customer on nil.
You can get around this using try (eg. violations.first.try(:customer)), or more correctly to check for the presence of any violations (eg. violations.first.customer if violations.any?).