This makes `ActionDispatch::Controller#content_type` return not only
the MIME type, but also in some circumstances the charset.
Example:
```ruby
reponse.content_type == 'text/html; charset=utf-8'
```
The MIME type-only fragment can now be accessed using `#media_type`.
Changes to the tests are not stricly necessary (because no charset is
present in the actual value), but represent the intent better.
Test helpers are separated between two files: spec_helper and
rails_helper. This separation is meant to allow tests that do not
require Rails (like testing standalone libs) to boot faster.
The spec_helper file is always loaded, through `--require spec_helper`
in the `.rspec` config file. When needed, the rails_helper file is
expected to be required manually.
This is fine, but:
- Many test files have a redundant `require 'spec_helper'` line;
- Many test files should require `rails_helper`, but don't.
Not requiring `rails_helper` will cause the Rails-concerned section of
the test environment not to be configured–which may cause subtle bugs
(like the test database not being properly initialized).
Moreover, Spring loads all the Rails files on preloading anyway. So the
gains from using only `spec_helper` are thin.
To streamline this process, this commit:
- Configures `.rspec` to require `rails_helper` by default;
- Remove all manual requires to spec_helper or rails_helper.
Reference: https://stackoverflow.com/questions/24145329/how-is-spec-rails-helper-rb-different-from-spec-spec-helper-rb-do-i-need-it
The specs sometime failes locally, because the order of the returned
objects is undefined.
This is an acceptable behavior – but it means we should test for
collection membership, rather than for a specific array order.
Replace `match` by `match_array` to have unordered matching.
