Accumulate: add test to forbid changing in place
Accumulate: add test to forbid changing in place

kickinbahk/xruby,rashmiagar/exercism,Insti/xruby,kotp/xruby,remcopeereboom/xruby,NeimadTL/ruby,rashmiagar/exercism,gchan/xruby,wobh/xruby,Calvyn82/xruby,wobh/xruby,Insti/exercism-ruby,jdsayle/xruby,NeimadTL/ruby,gchan/xruby,exercism/xruby,NobbZ/xruby,darrencauthon/xruby,Calvyn82/word_count,darrencauthon/xruby,NeimadTL/ruby,tommyschaefer/xruby,mamenama/xruby,alexbrinkman/xruby,Calvyn82/xruby,samilokan/xruby,exercism/xruby,jdsayle/xruby,Insti/exercism-ruby,samilokan/xruby,mamenama/xruby,kotp/xruby,remcopeereboom/xruby,tommyschaefer/xruby,Insti/xruby,alexbrinkman/xruby,Insti/exercism-ruby,dalexj/xruby,NobbZ/xruby,Calvyn82/word_count,dalexj/xruby,kickinbahk/xruby