ASSERT_EQ(0, GetGradDefs(gdef).size());

  // Make grad_func a gradient of func
  TF_GraphCopyFunction(host_graph_, func, grad_func, s_);
  ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);

  // Verify that function and its grad are linked
  gdef.Clear();
  GetGraphDef(host_graph_, &gdef);
  std::vector<std::pair<string, string>> grads = GetGradDefs(gdef);
  ASSERT_EQ(1, grads.size());