When your Rails application server raises error, Capybara will fail your test when it clears the session after the last step. The effect is a test that passes all steps, but fails anyway.

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Capybara's behavior will help you to detect and fix errors in your application code. However, sometimes your application will explode with an error outside your control. Two examples:

• A JavaScript library references a source map in its build, but forgets to package the source map
• CarrierWave cleans up an upload or cache file after the record was deleted / updated, and only then does the browser requests that image

Workaround

The code below patches Capybara to ignore errors with a given message. Adust the IGNORE_MESSAGE array for your application.

module IgnoreMissingStaticFiles

  # Adjust this list of regular expressions for your application
  IGNORE_MESSAGES = [
    # We have some JS libraries with missing source maps
    %r{No route matches .*"[^"]+\.map"}i,
    # CarrierWave may delete cache files before the browser tries to load them
    %r{No route matches .*"/uploads/test/\d+-[\d\-]+/[^"]+"}i,
  ].freeze

  def raise_server_error!
    super
  rescue StandardError => e
    # Ignore errors about missing source maps
    unless IGNORE_MESSAGES.any? { |ignore_message| e.message =~ ignore_message }
      raise e
    end
  end
end

Capybara::Session.class_eval do
  prepend IgnoreMissingStaticFiles
end