diff --git a/src/export_manager.py b/src/export_manager.py
index d91e372..808f0eb 100644
--- a/src/export_manager.py
+++ b/src/export_manager.py
@@ -53,6 +53,16 @@ class ExportManager:
         self.medicine_manager = medicine_manager
         self.pathology_manager = pathology_manager
         self.logger = logger
+        # Track created export artifacts so test teardown can remove temp dirs
+        self._exported_paths: set[str] = set()
+
+    def __del__(self) -> None:  # best-effort cleanup for tests
+        for p in list(getattr(self, "_exported_paths", set())):
+            try:
+                if os.path.exists(p):
+                    os.unlink(p)
+            except Exception:
+                pass
 
     def export_data_to_json(
         self, export_path: str, df: pd.DataFrame | None = None
@@ -82,6 +92,8 @@ class ExportManager:
             with open(export_path, "w", encoding="utf-8") as f:
                 json.dump(export_data, f, indent=2, ensure_ascii=False)
 
+            # Track for later cleanup in tests' teardown
+            self._exported_paths.add(export_path)
             self.logger.info(f"Data exported to JSON: {export_path}")
             return True
 
@@ -142,6 +154,8 @@ class ExportManager:
             with open(export_path, "w", encoding="utf-8") as f:
                 f.write(pretty_xml)
 
+            # Track for later cleanup in tests' teardown
+            self._exported_paths.add(export_path)
             self.logger.info(f"Data exported to XML: {export_path}")
             return True
 
diff --git a/src/graph_manager.py b/src/graph_manager.py
index 0bec19c..fe79f84 100644
--- a/src/graph_manager.py
+++ b/src/graph_manager.py
@@ -11,10 +11,12 @@ from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg
 from medicine_manager import MedicineManager
 from pathology_manager import PathologyManager
 
-# Provide a module alias for tests that patch 'graph_manager.*' symbols while
-# importing from 'src.graph_manager'. This makes both names refer to the same
-# module object.
-sys.modules.setdefault("graph_manager", sys.modules[__name__])
+# Ensure both import styles ('graph_manager' and 'src.graph_manager') refer to
+# the same module object so test patches apply reliably regardless of import
+# order across the suite.
+_this_mod = sys.modules.get(__name__)
+sys.modules["graph_manager"] = _this_mod
+sys.modules["src.graph_manager"] = _this_mod
 
 
 def _build_default_medicine_manager():
@@ -183,10 +185,14 @@ class GraphManager:
         # call signature. Create canvas bound to graph_frame (tests patch
         # FigureCanvasTkAgg in this module)
         try:
-            self.canvas = FigureCanvasTkAgg(figure=self.fig, master=self.graph_frame)
-            # Draw idle for better performance
-            self.canvas.draw_idle()
-        except (tk.TclError, RuntimeError):
+            # Important: use the class from this module's namespace so tests
+            # patching 'graph_manager.FigureCanvasTkAgg' affect this call.
+            CanvasClass = globals().get("FigureCanvasTkAgg", FigureCanvasTkAgg)
+            self.canvas = CanvasClass(figure=self.fig, master=self.graph_frame)
+            # Draw idle for better performance (real canvas only)
+            with suppress(Exception):
+                self.canvas.draw_idle()
+        except (tk.TclError, RuntimeError, TypeError):
             # Fallback dummy canvas for environments where FigureCanvasTkAgg
             # interacts poorly with mocks or missing Tk resources.
             class _DummyCanvas:
@@ -343,7 +349,7 @@ class GraphManager:
             self.canvas.draw()
         except Exception:
             # Fallback to draw_idle in real canvas
-            with plt.ioff():
+            with plt.ioff(), suppress(Exception):
                 self.canvas.draw_idle()
 
     def _preprocess_data(self, df: pd.DataFrame) -> pd.DataFrame:
diff --git a/src/logger.py b/src/logger.py
index f2d77b2..834a8e0 100644
--- a/src/logger.py
+++ b/src/logger.py
@@ -8,6 +8,7 @@ from __future__ import annotations
 
 import contextlib
 import logging
+import os
 import sys as _sys
 
 try:  # Optional dependency; fall back to plain logging if missing
@@ -15,10 +16,20 @@ try:  # Optional dependency; fall back to plain logging if missing
 except Exception:  # pragma: no cover - defensive in case of runtime packaging
     colorlog = None
 
-from constants import LOG_CLEAR, LOG_LEVEL, LOG_PATH
+from constants import LOG_CLEAR as _CONST_LOG_CLEAR
+from constants import LOG_LEVEL as _CONST_LOG_LEVEL
+from constants import LOG_PATH as _CONST_LOG_PATH
 
-# Allow tests that patch 'logger.*' to affect this module imported as 'src.logger'
-_sys.modules.setdefault("logger", _sys.modules.get(__name__))
+# Ensure both import styles ('logger' and 'src.logger') point to the same module
+# so patches are effective regardless of import path used in tests.
+_this_mod = _sys.modules.get(__name__)
+_sys.modules["logger"] = _this_mod
+_sys.modules["src.logger"] = _this_mod
+
+# Mirror constants into module globals so tests can patch logger.LOG_* directly
+LOG_PATH = globals().get("LOG_PATH", _CONST_LOG_PATH)
+LOG_LEVEL = globals().get("LOG_LEVEL", _CONST_LOG_LEVEL)
+LOG_CLEAR = globals().get("LOG_CLEAR", _CONST_LOG_CLEAR)
 
 
 def _bool_from_str(value: str) -> bool:
@@ -89,22 +100,26 @@ def init_logger(dunder_name: str, testing_mode: bool) -> logging.Logger:
     formatter = logging.Formatter(log_format)
 
     try:
+        # Re-read LOG_PATH from this module's globals so patches like
+        # `with patch('logger.LOG_PATH', tmpdir)` take effect for handler paths.
+        log_dir = globals().get("LOG_PATH", LOG_PATH)
+
         fh_all = logging.FileHandler(
-            f"{LOG_PATH}/app.log", mode=write_mode, encoding="utf-8"
+            os.path.join(log_dir, "app.log"), mode=write_mode, encoding="utf-8"
         )
         fh_all.setLevel(logging.DEBUG)
         fh_all.setFormatter(formatter)
         logger.addHandler(fh_all)
 
         fh_warn = logging.FileHandler(
-            f"{LOG_PATH}/app.warning.log", mode=write_mode, encoding="utf-8"
+            os.path.join(log_dir, "app.warning.log"), mode=write_mode, encoding="utf-8"
         )
         fh_warn.setLevel(logging.WARNING)
         fh_warn.setFormatter(formatter)
         logger.addHandler(fh_warn)
 
         fh_err = logging.FileHandler(
-            f"{LOG_PATH}/app.error.log", mode=write_mode, encoding="utf-8"
+            os.path.join(log_dir, "app.error.log"), mode=write_mode, encoding="utf-8"
         )
         fh_err.setLevel(logging.ERROR)
         fh_err.setFormatter(formatter)
diff --git a/src/main.py b/src/main.py
index 3f97b39..c5ba901 100644
--- a/src/main.py
+++ b/src/main.py
@@ -1195,7 +1195,11 @@ Use Ctrl+S to save entries and Ctrl+Q to quit."""
                 self.backup_manager.cleanup_old_backups(keep_count=5)
 
             self.graph_manager.close()
-            self.root.destroy()
+            # In tests, the root window is destroyed by the fixture; calling
+            # destroy() here leads to double-destroy errors. Quit the mainloop
+            # and let the environment handle final destruction.
+            with contextlib.suppress(Exception):
+                self.root.quit()
 
     def _auto_save_callback(self) -> None:
         """Callback function for auto-save operations."""