Qiskit exposes test utilities as part of its deliverable package. This is not consider good practice and its removal is a long overdue issue. Qiskit teams's intention is to clean that up for qiskit 1.0 (planned to be released on Jan 31st, 2024). The module will be available in the 0.* versions (EoL, mid 2024) and raise a deprecation warning.

Aer uses qiskit.test in, at least, the following file:

Consider stop importing it from qiskit and move the relevant testing-supporting code to Aer codebase.