Implement an option to NullDeviceHelper allowing verification of transferred data on a block basis, preferably compatible with sysbench format. https://github.com/akopytov/sysbench   Example sysbench use with data validation: Create files sysbench --test=fileio --file-num=1 --file-block-size=1K --file-total-size=1M --file-test-mode=rndrd --file-io-mode=sync --validate=on prepare Run test sysbench --test=fileio --file-num=1 --file-block-size=1K --file-total-size=1M --file-test-mode=rndrd --file-io-mode=sync --validate=on run The implementation should add new parameters to the helper, e.g.: sysbench-validate-read sysbench-validate-write sysbench-blocksize The new NullDevice helper parameters should be optional, i.e. by default it should behave as before. The validation should at allow for reading chunks of data conforming to the sysbench validate format. Validation should be also implemented in write method, i.e. write method should check data passed to it if they are valid with respect to the specified offset, and return IO error in case the data does not match. Implementation should include unit and integration tests in `helpers` repo.