@Override
    public int hashCode() {
        return Objects.hash(createdAt(), this.getClass().getName());
    }
@Test
    public void testHashCode() {
        final int hashA = new MigrationA().hashCode();
        final int hashB = new MigrationB().hashCode();
        final int hashAa = new MigrationA().hashCode();

        assertThat(hashA).isNotEqualTo(hashB);
        assertThat(hashA).isEqualTo(hashAa);
    }