REGISTER_OP("TestNonCommUnavailable")
    .Output("out: string")
    .Doc(R"doc(Test non-communication op throwing Unavailable error.)doc");

REGISTER_OP("TestCommUnavailable")
    .Output("out: string")
    .SetIsDistributedCommunication()
    .Doc(R"doc(Test communication op throwing Unavailable error.)doc");

// Kernel that throws an Unavailable error.

  TF_DeleteBuffer(t_buffer);
}

REGISTER_OP("TestOpWithNoGradient")
    .Input("x: T")
    .Output("y: T")
    .Attr("T: {float, double}")
    .Doc(R"doc(
Test op with no grad registered.

x: input
y: output
)doc")
    .SetShapeFn(tensorflow::shape_inference::UnknownShape);

class CApiGradientsTest : public ::testing::Test {
 protected:
  CApiGradientsTest()