### Question:
Row { public void changeColumnName(String oldName, String newName) { Column column = this.columnByName.remove(oldName); if (column == null) { return; } column.setName(newName); this.columnByName.put(newName, column); } Row(); void useMemory(Memory globalMemory); Object getColumnValue(String columnName); Column getColumnByName(String column); void findColumnsAndApply(Predicate<Column> predicate, Consumer<Column> modifier); void findColumnsAndChangeName(Predicate<Column> predicate, Function<Column, String> renamingFunction); Column getColumnByIndex(int index); Collection<Column> getColumns(); List<Column> getColumnsSortedByColumnIndex(); void changeColumnName(String oldName, String newName); Row addColumn(int index, String name, Object value); Row addColumn(Column column); Row addNullColumn(int index, String name); void transformColumn(String name, Function<Object, Object> transformer); int getNumberOfColumns(); Map<String, Optional<Object>> getColumnValues(); Set<String> getColumnNames(); Map<String, String> getColumnsAsString(); Row removeColumn(String name); String getDestination(String columnName); boolean isNumber(String column); boolean isString(String column); Row changeDestination(String column, String newDestination); boolean isEmpty(); List<String> getSortedColumnNames(); Map<String, Row> getColumnsGroupedByDestination(); Row convert(List<Map.Entry<String, Column>> content); boolean isColumnEmpty(String name); Row add(Row input); List<Row> getChildren(); boolean hasChildren(); Memory getMemory(); void successfullyProcessed(); void errorOccured(); void errorOccured(Throwable ex); void reindexColumns(); @Override String toString();  }### Answer:
@Test public void changeColumnName() { final String oldName = "duke"; this.cut.addColumn(0, oldName, "--any value--"); assertThat(this.cut.getNumberOfColumns(), is(1)); final String newName = "juggy"; this.cut.changeColumnName(oldName, newName); assertThat(this.cut.getNumberOfColumns(), is(1)); Column columnByName = this.cut.getColumnByName(newName); assertThat(columnByName.getName(), is(newName)); Column originColumn = this.cut.getColumnByName(oldName); assertNull(originColumn); }