code: @Test public void mongoIsUp() throws Exception {
    CommandResult commandResult=mock(CommandResult.class);
    given(commandResult.getString("version")).willReturn("2.6.4");
    MongoTemplate mongoTemplate=mock(MongoTemplate.class);
    given(mongoTemplate.executeCommand("{ buildInfo: 1 }")).willReturn(commandResult);
    MongoHealthIndicator healthIndicator=new MongoHealthIndicator(mongoTemplate);
    Health health=healthIndicator.health();
    assertEquals(Status.UP,health.getStatus());
    assertEquals("2.6.4",health.getDetails().get("version"));
    verify(commandResult).getString("version");
    verify(mongoTemplate).executeCommand("{ buildInfo: 1 }");
  }
  