def METHOD_NAME(self):
    """Test clearing a canvas."""
    o = self.dc.Line(10, 10, -200, -300)
    self.canvas.add(o)
    o2 = self.dc.Line(-10, -10, 200, 300)
    self.canvas.add(o2)
    self.canvas.delete_all_objects()
    assert o not in self.canvas
    assert o2 not in self.canvas