HTTP_ACCEPT header is missing in controller specs

[watcher...@gmail.com]

Hi.

Recently I discovered a starange thing. ActionDispatch::TestRequest instance doesn't contain HTTP_ACCEPT header while been generated in controller specs:

RSpec.describe "Projects", :type => :controller do
    describe FoosController do
        describe "Get index" do
            context "common" do
                before do
                    get :index, nil, {'HTTP_ACCEPT' => 'application/json'} #doesn't affect at all, nothing to affect
                end
                ...
             end
        end
    end
end

Hence it's impossible to set this header during requests. The only solution I found is setting the header with @request.env in before block before issuing the request:

before do
    @request.env['HTTP_ACCEPT'] = 'application/json'
    ...
end

Can anyone explain me why this is happening in controller specs? And is there another (better) way to set the header? 

ActionDispatch::TestRequest