I had a tough time testing login failures after the SSO integration with E-Business Suite. The login page does not reveal if it is an invalid User Name or an invalid Password. All i get is "Error: Authentication failed. Please try again".I turned to the $ORACLE_HOME/sso/log/ssoServer.log for help. The ssoServer.log provides additional error information only for invalid User Names. In the below error message, the stack trace reveals the problem is with the username email@example.com , meaning this username does not exist in the Oracle Internet Directory (and MS Active Directory).
Now, if i enter a valid User Name,but invalid password, Oracle fails to update ssoServer.log with any error/stack trace. Oracle keeps you guessing on this aspect.