### Question:
StreamConnectionManager { public StreamConnection openConnection(final StreamConnectionId streamConnectionId) { Objects.requireNonNull(streamConnectionId); return connections.computeIfAbsent(streamConnectionId, StreamConnection::new); }  StreamConnection openConnection(final StreamConnectionId streamConnectionId); Optional<StreamConnection> closeConnection(final StreamConnectionId streamConnectionId);  }### Answer:
@Test public void openConnection() { StreamConnectionId streamConnectionId = StreamConnectionId.of("foo"); final StreamConnection streamConnection = streamConnectionManager .openConnection(streamConnectionId); assertThat(streamConnectionManager.openConnection(streamConnectionId)).isEqualTo(streamConnection); assertThat(streamConnectionManager.openConnection(streamConnectionId)).isEqualTo(streamConnection); }