Add extra test case

Author: dstansby

lib/matplotlib/tests/test_image.py

@@ -370,6 +370,7 @@ def test_cursor_data():
     [[0.5, 0.5], 0 + 0],
     [[0.5, 1.5], 0 + 1],
     [[4.5, 0.5], 16 + 0],
+    [[8.5, 0.5], 16 + 0],
     [[9.5, 2.5], 81 + 4]
     ]
 )