Cách fix lỗi could not initialize proxy no session

Unable to reproduce, below is my test code:

public class LazeTest extends BaseCoreFunctionalTestCase {

@Entity
public static class A implements Serializable {
  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;
  private String firstName;
  private String lastName;
  private String code;
  private String fatherName;
  @Enumerated
  private PersonelKind kind;
  @ManyToOne(fetch = FetchType.LAZY)
  private B post;
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getCode() {
        return code;
    }
    public void setCode(String code) {
        this.code = code;
    }
    public String getFatherName() {
        return fatherName;
    }
    public void setFatherName(String fatherName) {
        this.fatherName = fatherName;
    }
    public PersonelKind getKind() {
        return kind;
    }
    public void setKind(PersonelKind kind) {
        this.kind = kind;
    }
    public B getPost() {
        return post;
    }
    public void setPost(B post) {
        this.post = post;
    }
}
public enum PersonelKind {
    A, B;
}
@Entity
@Cache(usage = CacheConcurrencyStrategy.READ_ONLY)
public static class B implements Serializable {
  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;
  private String firstName;
  private String lastName;
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
}
@Override
protected Class<?>[] getAnnotatedClasses() {
    return new Class[] { A.class, B.class };
}
@Override
protected void configure(Configuration cfg) {
    super.configure(cfg);
    cfg.setProperty(Environment.DRIVER, org.h2.Driver.class.getName());
    cfg.setProperty(Environment.URL, "jdbc:h2:mem:db1;DB_CLOSE_DELAY=-1;");
    cfg.setProperty(Environment.USER, "sa");
    cfg.setProperty(Environment.PASS, "");
    cfg.setProperty(Environment.CACHE_REGION_PREFIX, "");
    cfg.setProperty(Environment.GENERATE_STATISTICS, "true");
    cfg.setProperty(Environment.SHOW_SQL, "true");
    cfg.setProperty(Environment.USE_SECOND_LEVEL_CACHE, "true");
    cfg.setProperty(Environment.USE_QUERY_CACHE, "true");
    cfg.setProperty(Environment.CACHE_REGION_FACTORY, RedissonRegionFactory.class.getName());
}
@Before
public void before() {
    sessionFactory().getCache().evictEntityRegions();
    sessionFactory().getStatistics().clear();
}
@Test
public void test() {
    Session s = openSession();
    s.beginTransaction();
    A a = new A();
    a.setFatherName("nameA");
    B b = new B();
    b.setFirstName("nameB");
    a.setPost(b);
    s.save(b);
    Serializable id = s.save(a);
    s.flush();
    s.getTransaction().commit();
    s = openSession();
    s.beginTransaction();
    A a1 = s.load(A.class, id);
    assertThat(a1.getPost().getFirstName()).isEqualTo("nameB");
    s.getTransaction().commit();
}