Penetration tests are also used as a means to check the readiness of the support staff in responding to incidents and intrusion attempts. You should discuss this with the client whether it is an announced or unannounced test. If it's an announced test, make sure that you inform the client of the time and date, as well as the source IP addresses from where the testing (attack) will be done, in order to avoid any real intrusion attempts being missed by their IT security team. If it's an unannounced test, discuss with the client what will happen if the test is blocked by an automated system or network administrator. Does the test end there, or do you continue testing? It all depends on the aim of the test, whether it's conducted to test the security of the infrastructure or to check the response of the network security and incident handling team. Even if you are conducting an unannounced test, make sure that someone in the escalation matrix knows about the time and date of the test. Web application penetration tests are usually announced.