test(connection): manager unit tests with a fake poller — connect/reconnect backoff, TTL expiry, listeners, lifecycle

tests/conftest.py

@@ -3,10 +3,50 @@
 Puts the vendored ha_adb_common package on sys.path so helpers can be imported
 directly (their code is stdlib-only) without installing Home Assistant or
 executing the integration's __init__ module.
+
+The integration-package modules that stay Home-Assistant-free at import time
+(currently connection.py) are also made importable — via a synthetic package
+("nsh") that wraps custom_components/nvidia_shield WITHOUT executing its
+__init__.py (that one imports Home Assistant). Only the stdlib-only modules
+are loaded into it explicitly; their relative imports resolve normally.
 """
 
+import importlib.util
 import sys
+import types
 from pathlib import Path
 
 REPO_ROOT = Path(__file__).resolve().parent.parent
 sys.path.insert(0, str(REPO_ROOT / "custom_components" / "nvidia_shield"))
+
+_SHIELD_DIR = REPO_ROOT / "custom_components" / "nvidia_shield"
+_PKG = "nsh"
+
+
+def _load_module(name: str, path: Path, search_paths: list[str] | None = None):
+    """Import a source file under ``name`` without touching real packages."""
+    spec = importlib.util.spec_from_file_location(
+        name, path, submodule_search_locations=search_paths
+    )
+    module = importlib.util.module_from_spec(spec)
+    sys.modules[name] = module
+    spec.loader.exec_module(module)
+    return module
+
+
+# Synthetic integration package — no __init__.py execution (HA-free).
+_root = types.ModuleType(_PKG)
+_root.__path__ = [str(_SHIELD_DIR)]
+sys.modules[_PKG] = _root
+
+# Real subpackage __init__ (stdlib-only) so `from .ha_adb_common import ...`
+# works through the synthetic package.
+_load_module(
+    f"{_PKG}.ha_adb_common",
+    _SHIELD_DIR / "ha_adb_common" / "__init__.py",
+    [str(_SHIELD_DIR / "ha_adb_common")],
+)
+
+# Stdlib-only integration modules.
+for _mod in ("const", "adb_session", "connection"):
+    _load_module(f"{_PKG}.{_mod}", _SHIELD_DIR / f"{_mod}.py")