Rails，RSpec：如何测试，特定的邮件程序操作被触发

Question

I need to ensure that running an importer results in sending out an email.

This is what I got so far:

describe '#import' do
  it 'triggers the correct mailer and action', :vcr do
    expect(OrderMailer).to receive(:delivery_confirmation).with(order)

    Importer.new(@file).import
    remove_backed_up_file
  end
end

It fails with:

pry(#<ActiveRecord::ConnectionAdapters::TransactionManager>)> error
=> #<NoMethodError: undefined method `deliver_now' for nil:NilClass>

Which obviously can't work out as I am expecting the Mailer class to receive the (instance) method call. But how can I get a hold of the mailer instance that will receive the call? How would you test that a unit's method triggers a certain mailer?

Answer 1

I assume the delivery_confirmation method in reality returns a Mail object. The problem is that ActionMailer will call the deliver method of the mail object. You've set an expectation stubbing out the delivery_confirmation method but you haven't specified what should be the return value. Try this

mail_mock = double(deliver: true)
# or mail_mock = double(deliver_now: true)
expect(mail_mock).to receive(:deliver)
# or expect(mail_mock).to receive(:deliver_now)
allow(OrderMailer).to receive(:delivery_confirmation).with(order).and_return(mail_mock)
# the rest of your test code

Answer 2

If I got you right,

expect_any_instance_of(OrderMailer).to receive(:delivery_confirmation).with(order)

will test the mailer instance that will receive the call.

For more precision you may want to set up your test with the particular instance of OrderMailer (let's say order_mailer ) and write your expectation the following way

expect(order_mailer).to receive(:delivery_confirmation).with(order)