### Question:
Filter extends Operator { public TupleDesc getTupleDesc() { return iterator.getTupleDesc(); } Filter(Predicate p, DbIterator child); Predicate getPredicate(); TupleDesc getTupleDesc(); void open(); void close(); void rewind(); @Override DbIterator[] getChildren(); @Override void setChildren(DbIterator[] children);  }### Answer:
@Test public void getTupleDesc() { Predicate pred = new Predicate(0, Predicate.Op.EQUALS, TestUtil.getField(0)); Filter op = new Filter(pred, scan); TupleDesc expected = Utility.getTupleDesc(testWidth); TupleDesc actual = op.getTupleDesc(); assertEquals(expected.toString(), actual.toString()); }