### Question:
AgentSessionManager { public Host getHost(String sessionId) throws HostNotRegisteredException { Preconditions.checkNotNull(sessionId); Host host = registeredHosts.get(sessionId); if (host != null) { return host; } throw HostNotRegisteredException.forSessionId(sessionId); }  void register(String sessionId, Host host); boolean isRegistered(String sessionId); Host getHost(String sessionId); String getSessionId(Long hostId); void unregisterByHost(Long hostId);  }### Answer:
@Test(expected = HostNotRegisteredException.class) public void exceptionThrownForUnknownSessionId() throws HostNotRegisteredException { underTest.getHost("unknown session ID"); }