fixes #644

Author: jph00

fastcore/test.py

@@ -100,6 +100,7 @@ def test_warns(f, show=False):
 # %% ../nbs/00_test.ipynb
 def test_fig_exists(ax):
  "Test there is a figure displayed in `ax`"
+ if not hasattr(ax.figure.canvas, 'renderer'): ax.figure.canvas.draw()
  assert ax and len(ax.figure.canvas.tostring_argb())
 
 # %% ../nbs/00_test.ipynb