tests: add _() helper to generate mock path

tests/helpers.py

@@ -0,0 +1,14 @@
+def _(mock_path: str) -> str:
+    """Helper to simplify Mock path strings.
+
+    Args:
+        mock_path (str): The partial path to be appended to the standard prefix for mock paths.
+
+    Returns:
+        str: The full mock path combined with the standard prefix.
+
+    Example:
+        >>> _("module.Class.method")
+        "custom_components.econnect_metronet.module.Class.method"
+    """
+    return f"custom_components.econnect_metronet.{mock_path}"