test: Improve tests for submodule toolbox.enhanced

tests/test_toolbox/test_enhanced.py

@@ -1,9 +1,11 @@
 # pylint: disable=all
 
+import importlib
 import pathlib
 import platform
 import tkinter
 import unittest
+import unittest.mock
 
 from tkintertools.toolbox import enhanced
 
@@ -40,5 +42,41 @@ def test_resize(self) -> None:
         self.assertEqual(new_height, 100)
 
 
+@unittest.skipIf(platform.system() == "Linux", "No display name.")
+class TestPhotoImageNoPillow(unittest.TestCase):
+
+    def setUp(self) -> None:
+        with unittest.mock.patch.dict("sys.modules", {'PIL': None}):
+            importlib.reload(enhanced)
+
+        self.tk = tkinter.Tk()
+        self.image = enhanced.PhotoImage(file=pathlib.Path(__file__).parent.parent/"assets/images/logo.png")
+        self.width = self.image.width()
+        self.height = self.image.height()
+
+    def tearDown(self) -> None:
+        self.tk.destroy()
+        importlib.reload(enhanced)
+
+    def test_scale(self) -> None:
+        large_image = self.image.scale(1.5, 1.5)
+        small_image = self.image.scale(0.5, 0.5)
+        large_width = large_image.width()
+        large_height = large_image.height()
+        small_width = small_image.width()
+        small_height = small_image.height()
+        self.assertEqual(large_width, self.width*1.5)
+        self.assertEqual(large_height, self.height*1.5)
+        self.assertEqual(small_width, self.width*0.5)
+        self.assertEqual(small_height, self.height*0.5)
+
+    def test_resize(self) -> None:
+        new_image = self.image.resize(100, 100)
+        new_width = new_image.width()
+        new_height = new_image.height()
+        self.assertEqual(new_width, 100)
+        self.assertEqual(new_height, 100)
+
+
 if __name__ == "__main__":
     unittest.main()

tkintertools/toolbox/enhanced.py

@@ -12,10 +12,10 @@
 try:
     from PIL import ImageTk
 except ImportError:
-    pass
+    ImageTk = None
 
 
-if globals().get("ImageTk") is None:
+if ImageTk is None:
 
     class PhotoImage(tkinter.PhotoImage):
         """Enhanced version of `tkinter.PhotoImage`."""