Hello!

We are developing custom solution which is about to interact with Avaya via JTAPI.
Unfortunately, we have no access to working Avaya currently, thats why we try to find the way to test our solution with another way.
We found uot, that its possible to use Remote Lab 5 such as test environment, but it provide only success cases (like Call is active), but we need to test different scenarious (like user didnt answer, phone number invalid, etc..). Is it performable with this solution? Where exactly it is possible to learn from how to do it?

Thank you in advance!

the AES/CM remote lab will allow you to test a JTAPI application. However your choice of forums is inappropriate. ACE is a different product altogether.

Have you reviewed the information on this page
https://www.devconnectprogram.com/site/global/products_resources/avaya_aura_application_enablement_services/development_tools_configurations/aes_cm_remote_lab/index.gsp

along with downloading the user guides for the labs? If not please do, that will probably answer the majority of your questions. Additionally the labs are free, so there is no harm (other than time) in requesting a slot and playing around to see what is possible. Testing no answer, busy and other such scenarios is certainly possible.