Add new test with multiple writes for backends
Add new test with multiple writes for backends

bchapuis/restic,kurin/restic,jayme-github/restic,stuertz/restic,ckemper67/restic,stuertz/restic,middelink/restic,restic/restic,arithmetric/restic,kurin/restic,fawick/restic,fawick/restic,mappu/restic,byo/restic,restic/restic,middelink/restic,jayme-github/restic,ar-jan/restic,byo/restic,ar-jan/restic