Unfortunately, we do not provide permanent access to our test environment as we do not have any support team that looks after it. Our tech analysts in the Partner integration's team are assigned to help a number of partners that are currently developing and certifying to our API.
Our test environment is specifically built for testing purposes and thus the infrastructure is less robust than the live environment. Also, the traffic needs to be controlled to make sure that the test environment remains consistent for all partners running tests.
We do give the opportunity to our partners already live to have temporary access to it.