what is end-to-end Test ?

http://www.techopedia.com/definition/7035/end-to-end-test

Definition - What does End-to-End Test mean?

End-to-end testing is a methodology used to test whether the flow of an application is performing as designed from start to finish. The purpose of carrying out end-to-end tests is to identify system dependencies and to ensure that the right information is passed between various system components and systems.

Techopedia explains End-to-End Test

End-to-end testing involves ensuring that that integrated components of an application function as expected. The entire application is tested in a real-world scenario such as communicating with the database, network, hardware and other applications.

For example, a simplified end-to-end testing of an email application might involve:

Logging in to the application
Accessing the inbox
Opening and closing the mailbox
Composing, forwarding or replying to email
Checking the sent items
Logging out of the application