Using setFileDetector from Cucumber with Capybara

upload_a_file.rb

Given /^I upload (\w+)$/ do |filepath|
  # page.driver.browser gives you the Selenium object
  selenium = page.driver.browser
  
  selenium.file_detector = lambda do |args|
    # Capybara checks the file exists so we can just return the first argument, the file path
    args.first.to_s
  end
  
  # Scope to a specific form
  within("#form") do
    
    # file_input_locator can be a name, id or label of the file field
    attach_file ("file_input_locator", filepath)
  end