VacuumImpl extends BaseFinishedStatement implements Vacuum { @Nullable @Override public SqlPart previous() { return null; }  @Override void prependTo(@NotNull final RawSqlBuilder builder); @Nullable @Override SqlPart previous();  }
@Test public void previous_returnsNullValue() { VacuumImpl vacuum = new VacuumImpl(); SqlPart result = vacuum.previous(); assertThat(result, is(nullValue())); }