test: Cleaned up WriteBuffer unit test a bit
test: Cleaned up WriteBuffer unit test a bit

AndreasAakesson/IncludeOS,AnnikaH/IncludeOS,AnnikaH/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,mnordsletten/IncludeOS,alfred-bratterud/IncludeOS,AndreasAakesson/IncludeOS,ingve/IncludeOS,alfred-bratterud/IncludeOS,alfred-bratterud/IncludeOS,mnordsletten/IncludeOS,AnnikaH/IncludeOS,AndreasAakesson/IncludeOS,AnnikaH/IncludeOS,mnordsletten/IncludeOS,alfred-bratterud/IncludeOS,hioa-cs/IncludeOS,ingve/IncludeOS,ingve/IncludeOS,ingve/IncludeOS,ingve/IncludeOS,mnordsletten/IncludeOS,hioa-cs/IncludeOS,mnordsletten/IncludeOS,AnnikaH/IncludeOS,alfred-bratterud/IncludeOS,AndreasAakesson/IncludeOS,mnordsletten/IncludeOS,hioa-cs/IncludeOS