If clear it before the test, the mail of the last executed test will not
be correctly cleared.
Therefore, executing the test with seed below will result in an error.
```
./bin/test -w --seed 55480
Run options: --seed 55480
# Running:
...........................................................................................................................................................F
Failure:
MailDeliveryTest#test_does_not_increment_the_deliveries_collection_on_error [/home/yaginuma/program/rails/master_y_yagi/rails/actionmailer/test/delivery_methods_test.rb:221]:
--- expected
+++ actual
@@ -1 +1 @@
-[]
+[#<Mail::Message:47011389364640, Multipart: false, Headers: <Date: Mon, 14 Aug 2017 07:48:40 +0900>, <From: test-sender@test.com>, <To: test-receiver@test.com>, <Message-ID: <5990d748ea5b2_29342ac1af8bcf40886f7@yaginuma.mail>>, <Subject: Test Subject>, <Mime-Version: 1.0>, <Content-Type: text/plain>, <Content-Transfer-Encoding: 7bit>>]
bin/test test/delivery_methods_test.rb:216
```
Setting delivery_job on a mailer class will cause MessageDelivery to use
the specified job instead of ActionMailer::DeliveryJob:
class MyMailer < ApplicationMailer
self.delivery_job = MyCustomDeliveryJob
...
end
Currently `ActiveSupport::Duration` implicitly converts to a seconds
value when used in a calculation except for the explicit examples of
addition and subtraction where the duration is the receiver, e.g:
>> 2 * 1.day
=> 172800
This results in lots of confusion especially when using durations
with dates because adding/subtracting a value from a date treats
integers as a day and not a second, e.g:
>> Date.today
=> Wed, 01 Mar 2017
>> Date.today + 2 * 1.day
=> Mon, 10 Apr 2490
To fix this we're implementing `coerce` so that we can provide a
deprecation warning with the intent of removing the implicit coercion
in Rails 5.2, e.g:
>> 2 * 1.day
DEPRECATION WARNING: Implicit coercion of ActiveSupport::Duration
to a Numeric is deprecated and will raise a TypeError in Rails 5.2.
=> 172800
In Rails 5.2 it will raise `TypeError`, e.g:
>> 2 * 1.day
TypeError: ActiveSupport::Duration can't be coerced into Integer
This is the same behavior as with other types in Ruby, e.g:
>> 2 * "foo"
TypeError: String can't be coerced into Integer
>> "foo" * 2
=> "foofoo"
As part of this deprecation add `*` and `/` methods to `AS::Duration`
so that calculations that keep the duration as the receiver work
correctly whether the final receiver is a `Date` or `Time`, e.g:
>> Date.today
=> Wed, 01 Mar 2017
>> Date.today + 1.day * 2
=> Fri, 03 Mar 2017
Fixes#27457.
Follows the same pattern as controllers and jobs. Exceptions raised in
delivery jobs (enqueued by `#deliver_later`) are also delegated to the
mailer's rescue_from handlers, so you can handle the DeserializationError
raised by delivery jobs:
```ruby
class MyMailer < ApplicationMailer
rescue_from ActiveJob::DeserializationError do
…
end
```
ActiveSupport::Rescuable polish:
* Add the `rescue_with_handler` class method so exceptions may be
handled at the class level without requiring an instance.
* Rationalize `exception.cause` handling. If no handler matches the
exception, fall back to the handler that matches its cause.
* Handle exceptions raised elsewhere. Pass `object: …` to execute
the `rescue_from` handler (e.g. a method call or a block to
instance_exec) against a different object. Defaults to `self`.
They would be lost when the delivery job is enqueued, otherwise.
Prevents a common, hard-to-find bug like:
```ruby
message = Notifier.welcome(user, foo)
message.message_id = my_generated_message_id
message.deliver_later
```
The message_id is silently lost here! *Only the mailer arguments are
passed to the delivery job.*
This raises an exception now.
Make modifications to the message within the mailer method or use a
custom Active Job to manage delivery instead of using #deliver_later.
When #deliver_now is called all translations within the
generated email will be looked up for the current I18n
locale.
I18n.locale = ‘de’
mail.deliver_now # Generates german email, correct
In #enqueue_delivery the locale was not considered and
the resulting job uses the default locale.
I18n.locale = ‘de’
mail.deliver_later # Generate english email, incorrect
In order to achieve a consistent behaviour the current locale
is now always passed to `ActionMailer::DeliveryJob`.
Action Mailer tests weren't able to run in isolation without the bundle
exec prefix since we were requiring gems before requiring abstract_unit.
We don't need the `gem` call thus and the require_relative since the
test directory should be present in the load path when we run any test.
