The `ActiveJob::TestHelper` replace the adapter to test adapter in
`before_setup`. It gets the target class using the `descendants`, but if
the test target job class is not loaded, will not be a replacement of
the adapter.
Therefore, instead of replacing with `before_setup`, modified to
replace when setting adapter.

Fixes #26360

Refactored ActiveJob TestAdapter

Updated ActiveJob changelog

Fixed typo in changelog

Fixed formatting issue in changelog

Currently, backburner integration test is not running on CI.
https://travis-ci.org/rails/rails/jobs/196005322#L610

Using `Backburner::Worker.connection` to check whether beanstalkd is
running. But `Backburner::Worker.connection` was removed in backburner
1.2.0.
https://github.com/nesquena/backburner/commit/81fde499c2263abe8dedee59a3d0e03e92d72627

Therefore, this check process always becomes false, so the test is no
longer done. I fixed it so that check processing is done correctly.

[ci skip]

`InlineAdapter` is not used from 1f8558fa.

Actually, private methods cannot be called with `self.`, so it's not just redundant, it's a bad habit in Ruby

This reverts commit 1e969bfb, reversing
changes made to a5041f26.

Reason: It breaks the public API

If we create nested (namespaced) rails engine such like bukkits-admin,
`bin/rails g scaffold User name:string age:integer`
will create
`bukkits-admin/app/controllers/bukkits/users_controller.rb`
but it should create
`bukkits-admin/app/controllers/bukkits/admin/users_controller.rb`.

In #6643, we changed `namespaced_path` as root path
because we supposed application_controller is always in root
but nested rails engine's application_controller will not.

Per https://www.timeanddate.com/counters/firstnewyear.html, it's already
2017 in a lot of places, so we should bump the Rails license years to
2017.

[ci skip]

Currently it causes:

```
activejob/Rakefile:5: warning: already initialized constant ACTIVEJOB_ADAPTERS
```

Make sure the file doesn't exist until we've finished writing it.

This removes the following warnings.

```
/home/travis/build/rails/rails/activejob/lib/active_job/test_helper.rb:241: warning: shadowing outer local variable - job
/home/travis/build/rails/rails/activejob/lib/active_job/test_helper.rb:265: warning: shadowing outer local variable - job
```

Change ActiveJob::Base.queue_adapter to use queue_adapter method to make test code consistent.

If the deadlock has occurred `ActiveRecord::Deadlocked` will raise.
Ref: #25107, #26059

https://bugs.ruby-lang.org/issues/12739

`1-x-stable` branch does not exist, `master` is 1.x branch.
Ref: http://words.steveklabnik.com/rescuing-resque-again

`subclasses` get only child classes.
Therefore, if create a job common parent class as `ApplicationJob`,
inherited class does not get properly.

Usually users extends tests classes doing something like:

    ActionView::TestCase.include MyCustomTestHelpers

This is bad because it will load the ActionView::TestCase right aways
and this will load ActionController::Base making its on_load hooks to
execute early than it should.

One way to fix this is using the on_load hooks of the components like:

    ActiveSupport.on_load(:action_view) do
      ActionView::TestCase.include MyCustomTestHelpers
    end

The problem with this approach is that the test extension will be only
load when ActionView::Base is loaded and this may happen too late in the
test.

To fix this we are adding hooks to people extend the test classes that
will be loaded exactly when the test classes are needed.

If the deadlock has occurred `ActiveRecord::Deadlocked` will raise.
Ref: #25107, #26059

This will fix issues in [resque-scheduler](https://github.com/resque/resque-scheduler) `#job_to_hash` method,
so we can use `#enqueue_delayed_selection`, `#remove_delayed` method in resque-scheduler smoothly.

Yield the job instance so you have access to things like `job.arguments` on the custom logic after retries fail

Style/SpaceBeforeBlockBraces
Style/SpaceInsideBlockBraces
Style/SpaceInsideHashLiteralBraces

Fix all violations in the repository.

A few have been left for aesthetic reasons, but have made a pass
and removed most of them.

Note that if the method `foo` returns an array, `foo << 1`
is a regular push, nothing to do with assignments, so
no self required.