message: Test unit-length Concatenate input
diff: @@ -182,6 +182,10 @@ class MergeLayersTest(keras_parameterized.TestCase):
  concat_layer.compute_mask(
  [i1, i2], [K.variable(x1), K.variable(x2)]))))
  + # Should work with unit-length input.
  + unit_length_o = concat_layer([i1])
  + self.assertListEqual(unit_length_o.shape.as_list(), i1.shape.as_list())
  +
  with self.assertRaisesRegex(ValueError, '`mask` should be a list.'):
  concat_layer.compute_mask([i1, i2], x1)
  with self.assertRaisesRegex(ValueError, '`inputs` should be a list.'):
  