Suppose you have two resources routed in the following manner:

```ruby
resources :blogs do
  resources :posts
end

resources :posts
```

When using polymorphic resource routing like `url_for([@blog, @post])`, and `@blog` is `nil` Rails should still try to match the route to the top-level posts resource.

Fixes #16754

[ActionMailer] Rename test/test_test to test/test_case_test

[ci skip] add line about text layout

Sets the connection collation to the database collation configured
in database.yml. Otherwise, `SET NAMES utf8mb4` will use the default
collation for that charset (utf8mb4_general_ci) when you may have chosen
a different collation, like utf8mb4_unicode_ci.

This only applies to literal string comparisons, not column values, so
it is unlikely to affect you.

so this assertion causes random test fail

When we are loading a component and we want to know its version, we are
actually not speaking about the constant but the library itself.

[ci skip]

[Godfrey Chan & Xavier Noria]

Use system /tmp for temp files when testing actionpack

This was removed by mistake in 5e51bdda

`try` allocates an array on every call, we should avoid calling it in
hotspots.  This reduced AttributeMethodsTest#test_setting_time_zone_aware_attribute_with_string
from 18k allocations to 14k

We tenderized the wrong method! Object#try already had the yield option, just needed some tenderloving instance_eval to fit the bill

Fixed Active Job Backburner adapter

This fixes random test failure in migrator_test.rb

Make test:isolated run without bundler for Action Mailer

Avoid skipping Sidekiq tests on Rubinius

Now that Travis provides support for Rubinius 2.2.10, we can run the
Sidekiq tests against this version.

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.

Asserting that the message contains "QUERY PLAN" is enough for the adapter's test.
The plan may vary according to number of tuples etc. but that's out of our concern.

[ActiveJob] extract JobBuffer from helper

This reverts commit 16fe1983, reversing
changes made to 4c81c8ce.

The call to `Model.reset_column_information` was to express the intent of the test.
`reset_column_information` itself can trigger SQL queries because it checks
for a tables existance. Let's move it outside of the block.

/cc @sgrif

[ci skip] Fix example code of ActiveRecord::FixtureSet.context_class

Don't rescue IPAddr::InvalidAddressError

IPAddr::InvalidAddressError does not exist in Ruby 1.9.3
and fails for JRuby in 1.9 mode.

As IPAddr::InvalidAddressError is a subclass of ArgumentError
(via IPAddr::Error) just rescuing ArgumentError is fine.