Register a callable to decode rendered content for a given MIME type
Each registered decoder will also define a `#rendered.$MIME` helper
method, where `$MIME` corresponds to the value of the `mime` argument.
=== Arguments
`mime` - Symbol the MIME Type name for the rendered content
`callable` - Callable to decode the String. Accepts the String
value as its only argument
`block` - Block serves as the decoder when the
`callable` is omitted
By default, ActionView::TestCase defines a decoder for:
* :html - returns an instance of Nokogiri::XML::Node
* :json - returns an instance of ActiveSupport::HashWithIndifferentAccess
Each pre-registered decoder also defines a corresponding helper:
* :html - defines `rendered.html`
* :json - defines `rendered.json`
=== Examples
To parse the rendered content into RSS, register a call to `RSS::Parser.parse`:
```ruby
register_decoder :rss, -> rendered { RSS::Parser.parse(rendered) }
test "renders RSS" do
article = Article.create!(title: "Hello, world")
render formats: :rss, partial: article
assert_equal "Hello, world", rendered.rss.items.last.title
end
```
To parse the rendered content into a Capybara::Simple::Node,
re-register an `:html` decoder with a call to
`Capybara.string`:
```ruby
register_decoder :html, -> rendered { Capybara.string(rendered) }
test "renders HTML" do
article = Article.create!(title: "Hello, world")
render partial: article
rendered.html.assert_css "h1", text: "Hello, world"
end
```
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