Add some tests

tests/test_imshowtk.py

@@ -2,19 +2,38 @@
 
 from tkinter import Tk
 import cv2
-from imshowtk.imshowtk import bitmap_to_photo
+from imshowtk.imshowtk import bitmap_to_photo, ImshowTk
 
-def test_bitmap_to_photo():
-    """bitmap_to_photo runs"""
+def test_tk_is_working():
+    """On some macos runners TK doesn't get set up properly
+    We can quickly check for that here.
+    """
     try:
-        window = Tk(None)
+        _ = Tk(None)
     except RuntimeError:
         #we're getting runtime errors on some macos CI.
         #https://github.com/actions/setup-python/issues/649
         assert False
-        return
+
+def test_bitmap_to_photo():
+    """bitmap_to_photo runs"""
+    window = Tk(None)
     image = cv2.imread('project-icon.png')
     print (image.shape)
 
     _ = bitmap_to_photo(image)
     window.destroy()
+
+def test_mmshowtk_not_in_use():
+    """imshow does nothing if not in use"""
+    imshow = ImshowTk(in_use = False)
+    frame = cv2.imread('project-icon.png')
+    imshow.imshow(frame)
+    del imshow
+
+def test_imshowtk_in_use():
+    """imshow shows frame when in use"""
+    imshow = ImshowTk()
+    frame = cv2.imread('project-icon.png')
+    imshow.imshow(frame)
+    del imshow