### Question:
WhereHandler implements Handler { public void addFilter(String expression) throws ParseException { getClause().addElement(new ElementFilter(ExprUtils.parse(query, expression, true))); } WhereHandler(Query query);  WhereHandler(); Element getQueryPattern(); Query getQuery(); void addAll(WhereHandler whereHandler); Element getElement(); ElementGroup getClause(); void addWhere(TriplePath t); void addWhere(ValuesHandler values); void addOptional(TriplePath t); void addOptional(WhereHandler whereHandler); void addFilter(String expression); void addFilter(Expr expr); void addSubQuery(AbstractQueryBuilder<?> subQuery); ElementSubQuery makeSubQuery(AbstractQueryBuilder<?> subQuery); void addUnion(AbstractQueryBuilder<?> subQuery); void addGraph(Node graph, WhereHandler subQuery); void addGraph(Node graph, TriplePath subQuery); void addBind(Expr expr, Var var); void addBind(String expression, Var var); @Override void setVars(Map<Var, Node> values); @Override void build(); Node list(Object... objs); void addMinus( AbstractQueryBuilder<?> qb ); void addValueVar(PrefixMapping prefixMapping, Object var); void addValueVar(PrefixMapping prefixMapping, Object var, Object... objects); void addValueVars(PrefixMapping prefixMapping, Map<?,K> dataTable); void addValueRow(PrefixMapping prefixMapping, Object... values); void addValueRow(PrefixMapping prefixMapping, Collection<?> values); List<Var> getValuesVars(); Map<Var,List<Node>> getValuesMap(); void clearValues();  }### Answer:
@Test public void testAddFilter() throws ParseException { handler.addFilter("?one < 10"); handler.build(); assertContainsRegex(WHERE + OPEN_CURLY + "FILTER" + OPT_SPACE + OPEN_PAREN + var("one") + OPT_SPACE + LT + OPT_SPACE + "10" + CLOSE_PAREN + CLOSE_CURLY, query.toString()); }