title: How to order a list to do a unit test
body: <p>I have an test and when I do the expected in a Mock.perform, the list of "albuns" in the object "artista" are unordered and is the reason to broke my test.
  I just want to know if I can expect a list ordered by the id.</p>
  
  <p>In the "Artista.class" I have a HashSet and I tried but failed to do the conversion or compareTo.</p>
  
  <p>Please, sorry about my english and I expect that I was clear about the error. </p>
  
  <pre><code> @Test
  public void salvarArtistaComAlbuns() throws Exception {
  
      //instanciando albuns
      Album album1 = new Album();
      album1.setId(1L);
      album1.setNome("Raimundos");
      album1.setDescricao("Album de 2005");
  
      Album album2 = new Album();
      album2.setId(2L);
      album2.setNome("Raimundos2");
      album2.setDescricao("Album de 2008");
  
      //Inserindo albuns em um set de albuns
      Set&lt;Album&gt; albuns = new HashSet&lt;&gt;();
      albuns.add(album1);
      albuns.add(album2);
  
      //instanciando artista
      Artista artista = new Artista();
      artista.setId(1L);
      artista.setNome("Raimundos");
      artista.setDescricao("Rock brasileiro");
      artista.setAlbuns(albuns);
  
      //Convertendo artista em uma string para JSON
      String asJsonString = objectMapper.writeValueAsString(artista);
  
      //Chamando metodo save e definindo retorno
      when(artistaService.save(Mockito.any(Artista.class))).thenReturn(artista);
  
      //Mock do metodo post
      mockMvc.perform(
              MockMvcRequestBuilders.post("/artistas").contentType(MediaType.APPLICATION_JSON_UTF8_VALUE).accept(
                      MediaType.APPLICATION_JSON_UTF8_VALUE).content(asJsonString))
  
              .andExpect(status().isCreated()).andExpect(content().contentType(MediaType.APPLICATION_JSON_UTF8_VALUE))
  
              .andExpect(jsonPath("$.id", is(1))).andExpect(jsonPath("$.nome", is("Raimundos"))).andExpect(
                      jsonPath("$.descricao", is("Rock brasileiro")))
  
              .andExpect(jsonPath("$.albuns[1].id", is(1))).andExpect(
                      jsonPath("$.albuns[1].nome", is("Raimundos"))).andExpect(
                              jsonPath("$.albuns[1].descricao", is("Album de 2005")))
  
              .andExpect(jsonPath("$.albuns[2].id", is(2))).andExpect(
                      jsonPath("$albuns[2].nome", is("Raimundos2"))).andExpect(
                              jsonPath("$.albuns[2].descricao", is("Album de 2008")));
  
      //Verifica se o metodo SAVE foi chamado
      verify(artistaService, times(1)).save(Mockito.any(Artista.class));
      verifyNoMoreInteractions(artistaService);
  
      assertNotNull(artista.getId());
      assertThat(artista.getNome(), is("Raimundos"));
      assertThat(artista.getDescricao(), is("Rock brasileiro"));
  
      assertNotNull(album1.getId());
      assertThat(album1.getNome(), is("Raimundos"));
      assertThat(album1.getDescricao(), is("Album de 2005"));
  
      assertNotNull(album2.getId());
      assertThat(album2.getNome(), is("Raimundos2"));
      assertThat(album2.getDescricao(), is("Album de 2008"));
  
      assertEquals(albuns.size(), 2);
  
  }
  </code></pre>