'Merge should work with sparse.
GH-2295
GH-2155'

def test_sparse(self):

    data = Table('iris')[::25]
    data_ed_dense = Table('titanic')[::300]
    data_ed_sparse = Table('titanic')[::300]
    data_ed_sparse.X = sp.csr_matrix(data_ed_sparse.X)
    self.send_signal('Data', data)
    self.send_signal('Extra    Data', data_ed_dense)
    output_dense = self.get_output('Data')
    self.assertFalse(sp.issparse(output_dense.X))
    self.assertFalse(output_dense.is_sparse())
    self.send_signal('Extra    Data', data_ed_sparse)
    output_sparse = self.get_output('Data')
    self.assertTrue(sp.issparse(output_sparse.X))
    self.assertTrue(output_sparse.is_sparse())
    output_sparse.X = output_sparse.X.toarray()
    self.assertTablesEqual(output_dense, output_sparse)
