Move this

lib/slack_mattermost_emoji/slack_client.rb

       @log = log
       @authenticated = false
 
+      if [@username, @password, @domain].any? { |el| el.nil? || el.empty? }
+        raise 'Slack username, password, and domain are all required'
+      end
+
       Dir.mkdir(@download_path) unless Dir.exist?(@download_path)
 
       options = Selenium::WebDriver::Chrome::Options.new
       options.headless! unless headless == false
       @driver = Selenium::WebDriver.for :chrome, options: options
-
-      if [@username, @password, @domain].any? { |el| el.nil? || el.empty? }
-        raise 'Slack username, password, and domain are all required'
-      end
     end
 
     def authenticate