refactor(tests): ensure BEC dispatcher singleton object is renewed at each test

and add a check for dangling threads

tests/conftest.py

@@ -0,0 +1,32 @@
+import pytest
+import threading
+
+from bec_widgets.utils import bec_dispatcher as bec_dispatcher_module
+
+
+@pytest.fixture()
+def threads_check():
+    current_threads = set(
+        th
+        for th in threading.enumerate()
+        if "loguru" not in th.name and th is not threading.main_thread()
+    )
+    yield
+    threads_after = set(
+        th
+        for th in threading.enumerate()
+        if "loguru" not in th.name and th is not threading.main_thread()
+    )
+    additional_threads = threads_after - current_threads
+    assert (
+        len(additional_threads) == 0
+    ), f"Test creates {len(additional_threads)} threads that are not cleaned: {additional_threads}"
+
+
+@pytest.fixture(autouse=True)
+def bec_dispatcher(threads_check):
+    bec_dispatcher = bec_dispatcher_module.BECDispatcher()
+    yield bec_dispatcher
+    bec_dispatcher.disconnect_all()
+    # reinitialize singleton for next test
+    bec_dispatcher_module._bec_dispatcher = None