Rails 4.2 Mailer Problem

Since we updated our application to Rails 4.2, our mailer tests seems to fail (or not) randomly.

Simplified mailer code:

class ReservationMailer < ActionMailer::Base
default from: ‘no-reply@1.de’,
bcc: ‘kopie@1.de’

def reservation_received(reservation)
@reservation = reservation
@product = reservation.product

mail to: @reservation.email,


Simplified test code:

reservation = Reservation.new(email: ‘max@mustermann.com’, product: product)

email = ReservationMailer.reservation_received(reservation).deliver_now

assert_equal 1, ActionMailer::Base.deliveries.size

There are some more mailers very similar to this mailer and the tests seem to fail randomly.

That means, sometimes just one of these tests fail, sometimes two and somewhen nothing fails.

I couldn’t figure out any problem, but maybe you can help me out :slight_smile:

No one has an idea?