This will silence deprecation warnings.

Most of the test can be changed from `render :text` to render `:plain`
or `render :body` right away. However, there are some tests that needed
to be fixed by hand as they actually assert the default Content-Type
returned from `render :body`.

This is another take at #14384 as we decided to wait until `master` is
targeting Rails 5.0. This commit is implementation-complete, as it
guarantees that all the public methods on the hash-inherited Parameters
are still working (based on test case). We can decide to follow-up later
if we want to remove some methods out from Parameters.

We should use rack-test's upload file objects on the test side so that
we will be able to correctly generate mime blob posts in the future

We should convert request parameters to a query string, then let the
request object parse that query string.  This should give us results
that are more similar to the real-world

We should assign parameters to the request object rather than mutate the
hash that is returned by `query_parameters` or `request_parameters`

Instead of trying to manually clear out a request object, lets just
allocate a new one.  The rack ENV is reused and cleaned (still), but the
request object is not.

We should leverage the request / response objects that the superclass
has already allocated for us.

`head` method works similar to `render` method with `:nothing` option

+ To avoid regression I am adding this test case on action pack

Changed to assert from assert_equal

+ Added msg to assertion

Modified msg

Fixes regression in #18423. Merge default headers for new responses,
but don't merge when creating a response from the last session request.

hat tip @senny ❤

in `ActionController::TestCase` and
`ActionDispatch::Integration`

Old syntax:

    `xhr :get, :create, params: { id: 1 }`

New syntax example:

    `get :create, params: { id: 1 }, xhr: true`

Non-kwargs requests are deprecated now.
Guides are updated as well.

`post url, nil, nil, { a: 'b' }` doesn't make sense.
`post url, params: { y: x }, session: { a: 'b' }` would be an explicit way to do the same

Inside a controller functional test after the last flash is deleted it
still persists the flash because to_session_value is nil. We should
delete it from the session when the serialized version is nil, same as
the flash middleware.

Reference #17453

Reference #17453

[Godfrey Chan, Washington Luiz]

This reverts commit f93df528, reversing
changes made to a455e3f4.

Conflicts:
	actionpack/lib/action_controller/test_case.rb
	actionview/lib/action_view/test_case.rb

Follow up to 212057b9. Since that commit, we need to pass the `route_name`
explicitly. This is one of the left-over cases that was not handled in that
commit, which was causing `use_route` to be ignored in functional tests.

Hash#keys.each allocates an array of keys; Hash#each_key iterates through the
keys without allocating a new array. This is the reason why Hash#each_key
exists.

This pull request is a continuation of https://github.com/rails/rails/commit/925bd975 and https://github.com/rails/rails/commit/8d8ebe3d.

This is the continuation of the work started at
9d62e048

Commit 4f2cd3e9 introduced a bug by reordering the call to
`@controller.recycle!` above the call to `build_request_uri`. The
impact of this was that the `@_url_options` cache ends up not being
reset between building a request URI (occurring within the test
controller) and the firing of the actual request.

We encountered this bug because we had the following setup:

  class MinimumReproducibleController < ActionController::Base
    before_filter { @param = 'param' }

    def index
      render text: url_for(params)
    end

    def default_url_options
      { custom_opt: @param }
    end
  end

  def test_index
    get :index # builds url, then fires actual request
  end

The first step in  `get :index` in the test suite would populate the
@_url_options cache. The subsequent call to `url_for` inside of the
controller action would then utilize the uncleared cache, thus never
calling the now-updated default_url_options.

This commit fixes this bug calling recycle! twice, and removes a call
to set response_body, which should no longer be needed since we're
recycling the request object explicitly.

The request attributes filtered_parameters, filtered_env and filtered_path
are memoized for performance reasons. However this can cause unusual
behavior in tests where there are multiple calls to get, post, etc.

Fixes #13803.

JSON.{dump,generate} offered by the JSON gem is not compatiable with
Rails at the moment and can cause a lot of subtle bugs when passed
certain data structures. This changed all direct usage of the JSON gem
in internal Rails code to always go through AS::JSON.{decode,encode}.

We also shouldn't be implementing `to_json` most of the time, and
these occurances are replaced with an equivilent `as_json`
implementation to avoid problems down the road.

See [1] for all the juicy details.

[1]: intridea/multi_json#138 (comment)

This reverts commit 0303c232.

Conflicts:
	actionpack/lib/action_controller/test_case.rb

REASON: It will conflict with a lot of test cases. Better to call
`process` directly since this is a very uncommon HTTP method.

Fixes #10638.

The env hash passed to `Http::Headers#new` must be in env format.
Also be aware that the passed hash is modified directly.

docs and test-cases for setting headers/env in functional tests.

Follow up to #9700.

This commit changes route defaults so that explicit defaults are no
longer required where the key is not part of the path. For example:

  resources :posts, bucket_type: 'posts'

will be required whenever constructing the url from a hash such as a
functional test or using url_for directly. However using the explicit
form alters the behavior so it's not required:

  resources :projects, defaults: { bucket_type: 'projects' }

This changes existing behavior slightly in that any routes which
only differ in their defaults will match the first route rather
than the closest match.

Closes #8814

They don't add any benefits over `assert object.blank?`
and `assert object.present?`