How to test a web service?

Can you direct me to learn how to test the return of a service.

Context explication

the present case, I enter values ​​in the inputs but when I want to validate them, I have a warnning message “items not saved”
and KS marks that my test is successful, and yet no … :somnolent:

this is after i add the value, and i just can to catch this screen shoot

I did the test in step by step mode while waiting for loading, but again it is not good.
So it’s not a loading problem.

What is strange is when I do exactly the same procedure without going through KS, it works, my values ​​are well taken into account.

I do not understand why ?