Need help with RSpec xhr request

Rails
1

I have the following function in JS for a drag and drop file uploader:

function uploadFile(file){

         var xhr = new XMLHttpRequest();
         var upload = xhr.upload;
         var uri      =

“/imagebooks/upload_supporting_image/?authenticity_token=” +
$(‘meta[name=csrf-token]’).attr(“content”);

         xhr.open('POST', uri, true);
         xhr.setRequestHeader('X-Filename', file.fileName);

         xhr.send(file);


}

This works properly. I’m trying to create a spec to test the function
with rspec- anyone know how I can mimic this? I’ve tried:

before(:each) do
@image = File.open("#{Rails.root}/public/images/test/test.jpg",
‘rb’)

end

describe ‘Upload Supporting Image method’ do
it ‘should read a binary string and write a file with it’ do
request.env[‘X-Filename’] = ‘test.jpg’
xhr :post, :upload_supporting_image, @image
end
end

But it doesn’t work as expected. Any help is greatly appreciated!