Add skeleton unit test re #6896

Just tests initialization of the algorithm.

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>
Add test of file properties re #6898

and actually include the ModifyDetectorDotDatFileTest.h

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>
Add all testing but contents of output file re #6986

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>