End to End Testing is the approach in which tester/developer always validate whether the flow of application/software from the starting point to the end point is working perfectly or not.
End to End Testing Example - Real
For Example we are testing the web page of application than the start point will be logging in to web page and the end point will be logout of the web page means logout from the application/software.
So in this example of End to End Testing, tester/developer check whether the flow of application from starting to end point is working fine or not.
So in the above example when we login to the web page than tester/developer check that after login flow is properly working or not like they check after login we get into home page or not, they also check after login we are able to do some work or not, and finally they check after doing some little bit work we are able to logout from the application or not. So this is the End to End testing of web page performed by Developer/Tester, in which they check the complete flow of application from starting to end point.
Another Example of End to End Testing
Let’s take another example of this testing which is given below:
Suppose you are logging in to Gmail than End to End Testing is that after login you get into inbox or not, you are able to open and compose a mail or not, you are able to forward the mail or not, then finally you are able to logout from the Gmail or not. So this is the End to End Testing of Gmail in which tester check the flow of Gmail from starting to end point means from logging to logout point.
At end we conclude that End to End Testing is considered as the part of System Testing, and this testing is always conducted (carried out) to validate the flow of data between different modules. And you may also note that this testing is obviously conducted before closing the testing.