Function checkConstSliceIterator

unitTests/test_slice.cpp:206–210

 */
template <typename T>
void checkConstSliceIterator(const Slice<T>& sl, typename Slice<T>::value_type first_value) {
  for (auto it = sl.cbegin(); it < sl.cend(); ++it) {
    ASSERT_EQ(*it, first_value++);
  }
}

template <typename T>
void checkSubSlice(const Slice<T>& sl) {