message: Verifies that we can compute gradients through STFT
diff: @@ -27,6 +27,7 @@ from tensorflow.compiler.tests.xla_test import XLATestCase
  from tensorflow.contrib.signal.python.ops import spectral_ops as signal
  from tensorflow.python.framework import dtypes
  from tensorflow.python.ops import array_ops
  +from tensorflow.python.ops import gradients_impl
  from tensorflow.python.ops import spectral_ops
  from tensorflow.python.platform import googletest
  @@ -97,8 +98,11 @@ class FFTTest(XLATestCase):
  ph = array_ops.placeholder(
  dtypes.as_dtype(data.dtype), shape=data.shape)
  out = signal.stft(ph, ws, hs)
  + grad = gradients_impl.gradients(out, ph,
  + grad_ys=array_ops.ones_like(out))
  - value = sess.run(out, {ph: data})
  + # For gradients, we simply verify that they compile & execute.
  + value, _ = sess.run([out, grad], {ph: data})
  self.assertAllClose(expected, value, rtol=RTOL, atol=ATOL)
  def testFFT(self):
  