ASSERT_TRUE(worker_server2->Start().ok());
  const char dev2_name[] = "/job:localhost/replica:0/task:2/device:CPU:0";

  if (inject_error) {
    // Inject a function optimization pass failure when it sees the
    // 'read0_maybe_with_graph_error' op having a requested device `dev2_name`.
    // During execution:
    //   * task:0 processes main function `VariableAddFunctionWithGraphError`

  }

 private:
  TFE_Context* context_;
  TFE_CustomDevice device_;
  void* info_;
  string name_;
};

// An adapter which wraps the shape/data produced by C custom devices and uses
// it to implement custom device methods.
class CAPICustomDeviceTensorHandle
    : public tensorflow::CustomDeviceTensorHandle {
 public:
  CAPICustomDeviceTensorHandle(tensorflow::ImmediateExecutionContext* context,