Rails 4, RSpec 3.2 - how to mockup ActionMailer's deliver_now method to raise exceptions - actionmailer

Question

Environment
Ruby 2.2.1, Rails 4.2.0, rspec-core 3.2.2, rspec-expectations 3.2.0, rspec-mocks 3.2.1, rspec-rails 3.2.1, rspec-support 3.2.2
I have the following method
def send_event_alert_email(event_id)
event = Event.find_by(id: event_id)
...
...
...
EventAlertMailer.event_alert(event_id).deliver_now
create_alert(event)
end
I need to write specs which makes sure that create_alert(event) doesn't get invoked when EventAlertMailer.event_alert(event_id).deliver_now raises any exceptions. So the basic question is how do I simulate deliver_now to raise possible exceptions which it might actually throw.

Answer 1

Here is how to test deliver_now method:
describe EventAlertMailer do
it 'sends email' do
delivery = double
expect(delivery).to receive(:deliver_now).with(no_args)
expect(EventAlertMailer).to receive(:event_alert)
.with(event_id)
.and_return(delivery)
MyClass.send_event_alert_email
end
end