Add masked value formatting test

dstansby · dstansby · commit 2b02440f6da8 · 2019-08-27T10:46:37.000+01:00
diff --git a/lib/matplotlib/tests/test_image.py b/lib/matplotlib/tests/test_image.py
@@ -1103,3 +1103,18 @@ def test_respects_bbox():
     buf_after = io.BytesIO()
     fig.savefig(buf_after, format="rgba")
     assert buf_before.getvalue() != buf_after.getvalue()  # Not all white.
+
+
+def test_image_cursor_formatting():
+    fig, ax = plt.subplots()
+    # Create a dummy image to be able to call format_cursor_data
+    im = ax.imshow(np.zeros((4, 4)))
+
+    data = np.ma.masked_array([0], mask=[True])
+    assert im.format_cursor_data(data) == '[]'
+
+    data = np.ma.masked_array([0], mask=[False])
+    assert im.format_cursor_data(data) == '[0]'
+
+    data = np.nan
+    assert im.format_cursor_data(data) == '[nan]'
