how can I test all different kinds of errors?

[loryhoush1]

for example, like 

  -- communication: internet connection failed 
  -- communication: remote host not responding 
  -- authentication: my app id not recognized by remote host 
  -- authorization: cc account not recognized by authorize.net 
  -- financial: insufficient funds 

[TJPride]

See this from the FAQ:
http://developer.authorize.net/faqs/#specerrors

Basically, you use card number 4222222222222 and then an x_amount equal to the error code you want to get back.