std::uniform_int_distribution<> distribution;
    rng_val_ = distribution(gen);
  }

  static void SetCloudPath(const std::string& cloud_path) {
    cloud_path_ = cloud_path;
    if (cloud_path_.back() == '/') cloud_path_.pop_back();
  }

  static void SetTmpDir(const std::string& tmp_dir) {
    tmp_dir_ = tmp_dir.empty() ? ::testing::TempDir() : tmp_dir;
  }

 protected:
  Env* env_;

 private:

    if (TF_GetCode(status.get()) != TF_OK) {
      ADD_FAILURE() << tag << " -- " << TF_Message(status.get());
      continue;
    }
    TFE_DeleteTensorHandle(hdevice);
    // Copy back to CPU
    TFE_TensorHandle* hcopy =
        TFE_TensorHandleCopyToDevice(hdevice2, ctx, kCPUDevice, status.get());
    if (TF_GetCode(status.get()) != TF_OK) {
      ADD_FAILURE() << tag << " -- " << TF_Message(status.get());

      src.flat<tstring>()(i) = data[i];
    }
    TF_Tensor* dst = TF_TensorFromTensor(src, &status);
    ASSERT_TRUE(status.ok()) << status.message();

    // Convert back to a C++ Tensor and ensure we get expected output.
    Tensor output;
    ASSERT_EQ(absl::OkStatus(), TF_TensorToTensor(dst, &output)) << line;
    ASSERT_EQ(src.NumElements(), output.NumElements()) << line;

const char* kNegStackToString = "File \"neg.cc\", line 15, in beta";

std::vector<IOSpec> M(const std::initializer_list<string>& names) {
  std::vector<IOSpec> v;
  for (const string& name : names) {
    v.push_back(IOSpec(name, DT_INVALID));
  }
  return v;
}

// Specification for an expected edge.
// src is either:
// - input name (as it appears in FunctionDef)
// - name of output tensor (in nested "add:z:0" format)

///
/// The `TF_InitPlugin` function is used by plugins to set up the data
/// structures that implement this interface, as presented in Section 2. In
/// order to not have plugin shared objects call back symbols defined in core
/// TensorFlow, `TF_InitPlugin` has a `TF_FilesystemPluginInfo` argument which
/// the plugin must fill (using the `TF_SetFilesystemVersionMetadata` for the