'Show warning msg when data is sparse.
GH-2298
GH-2163'

def test_sparse_data(self):

    data = Table('iris')[::25]
    data.X = sp.csr_matrix(data.X)
    self.send_signal(self.widget.Inputs.data, data)
    self.assertTrue(self.widget.Warning.sparse_not_supported.is_shown())
    self.send_signal(self.widget.Inputs.data, None)
    self.assertFalse(self.widget.Warning.sparse_not_supported.is_shown())
