Do not use this function in production code. For use in **unit tests**.
This function initialises a new [[SolidDataset]] with metadata as though the
SolidDataset has been retrieved from the given URL. The mock SolidDataset can be used in
unit tests that require persisted SolidDatasets; e.g., unit tests that call [[getSourceUrl]].
This function initialises a new [[SolidDataset]] with metadata as though the SolidDataset has been retrieved from the given URL. The mock SolidDataset can be used in unit tests that require persisted SolidDatasets; e.g., unit tests that call [[getSourceUrl]].