Test manager class is a singleton

src/aiida/manage/configuration/__init__.py

@@ -57,7 +57,6 @@
 
 if TYPE_CHECKING:
     from aiida.orm import User
-
     from .config import Config
 
 # global variables for aiida

tests/manage/test_manager.py

@@ -32,3 +32,33 @@ def test_disconnect():
     assert node.is_finished_ok
     assert result == 2
     manager.reset_profile()  # This hangs before timing out
+
+@pytest.mark.requires_rmq
+def test_singleton():
+    """Test the communicator disconnect.
+
+    When the dependency ``kiwipy`` was updated to v0.8, it introduced a problem with shutting down the communicator.
+    After at least one process would have been run, trying to disconnect the communcitor would time out. The problem
+    is related to the update of the lower lying libraries ``aio-pika`` and ``aiormq`` to v9.4 and v6.8, respectively.
+    After much painstaking debugging the cause could not be determined, nor a solution. This test is added to
+    demonstrate the problematic behavior. Getting the communicator and then disconnecting it (through calling
+    :meth:`aiida.manage.manager.Manager.reset_profile`) works fine. However, if a process is a run before closing it,
+    for example running a calcfunction, the closing of the communicator will raise a ``TimeoutError``.
+    """
+    from aiida.manage import get_manager
+    from aiida.manage.manager import Manager
+
+    manager = get_manager()
+    manager2 = Manager()
+
+    print(manager)
+    print(manager2)
+
+    # manager.get_communicator()
+    # manager.reset_profile()  # This returns just fine
+    #
+    # result, node = add_calcfunction.run_get_node(1)
+    # assert node.is_finished_ok
+    # assert result == 2
+    # manager.reset_profile()  # This hangs before timing out
+