message: Add test case for GitHub issue 26879
diff: @@ -31,6 +31,7 @@ from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import random_ops
  from tensorflow.python.ops import resource_variable_ops
  +from tensorflow.python import keras
  class Tests(test.TestCase):
  @@ -228,6 +229,12 @@ class Tests(test.TestCase):
  self.assertTrue(ctx.has_function(f.get_concrete_function().name))
  + def testEagerExecute_InvalidType(self):
  + # Test case for GitHub issue 26879.
  + value = keras.layers.Input((128, 128, 1), dtype='float32')
  + with self.assertRaisesRegexp(TypeError, "Expected list for 'values' argument"):
  + _ = array_ops.stack(value, axis=1)
  +
  if __name__ == "__main__":
  test.main()
  