Add test for once without callback.
Add test for once without callback.

ebsco/backbone,dillonforrest/backbone-df,premkumargithub/backbone,gougouGet/backbone,chyeh727/backbone,huanglp47/backbone,wushuyi/backbone,wjb12/backbone,huanglp47/backbone,tadwhitaker/backbone,pandoraui/backbone,pandoraui/backbone,Aplopio/backbone,ohbarye/backbone,Flip120/backbone,JesseQin/backbone,webcoding/backbone,LovelyL25/backbone.js,ThisIsManta/Backbone,JesseQin/backbone,jewsroch/backbone,feychenie/backbone,linalu1/backbone,batigoal1980/backbone_example,webapp/library,gmaclennan/backbone,Connectlegendary/backbone,wangcan2014/backbone,zhangwei001/backbone,tibic/backbone,linalu1/backbone,oss-practice/backbone,Krasnyanskiy/backbone,7213/backbone,jmeas/backbone,tadwhitaker/backbone,jridgewell/backbone,alekskorolev/lightbones,GrimDerp/backbone,LovelyL25/backbone.js,zhangwei001/backbone,heroazure/backbone,vin100bk/backbone,nikolas/backbone,feychenie/backbone,nikolas/backbone,Khan/backbone,megawac/backbone,platinumazure/backbone,gougouGet/backbone,mpapp/backbone,Diwahars/backbone,cgvarela/backbone,ThisIsManta/Backbone,fanhc019/backbone,wushuyi/backbone,luffy94608/backbone,sunday-star/backbone,anhtholee/backbone,getshuvo/backbone,jstrimpel/backbone,embarknow/backbone,udhayam/backbone,rashmisajjan/backbone,heroazure/backbone,ereddate/backbone,Bug2014/backbone,tzkKrbys/backbone,gitterHQ/backbone,dcheepurupalli/backbone,trizko/backbone,Niades/backbone,trizko/backbone,componentizr/backbone,gdi2290/backbone,zgl2007dj/backbone,FishbaitHarry/backbone,wangdahoo/backbone,7213/backbone,lujocom/backbone,premkumargithub/backbone,dillonforrest/backbone-df,wxmfront/backbone,darrrk/backbone,wakanpaladin/mybackbone,honger05/backbone,yawenl/backbone,braddunbar/backbone,wxmfront/backbone,akre54/backbone,akre54/backbone,Krasnyanskiy/backbone,ntgn81/backbone,embarknow/backbone,npmcomponent/jashkenas-backbone,jstrimpel/backbone,elma-cao/backbone,ppker/backbone,youprofit/backbone,wjb12/backbone,luffy94608/backbone,IsoldaJS/isolda-models,mrblueblue/backbone,kuychaco/backbone,webapp/library,Khan/backbone,IsoldaJS/isolda-pubsub,sitexa/backbone,rashmisajjan/backbone,yuhualingfeng/backbone,ntgn81/backbone,zgl2007dj/backbone,GerHobbelt/backbone,ohbarye/backbone,Akkuma/backbone,ridixcr/backbone,mmolinastudio/backbone,ridixcr/backbone,jungjung917/backbone,dillonforrest/backbone-df,hugohua/backbone,maryrosecook/backbone-df,Bug2014/backbone,dcheepurupalli/backbone,zdespolit/backbone,nvoron23/backbone,udhayam/backbone,DannyDelott/backbone,jmeas/backbone,maryrosecook/backbone-df,lastjune/backbone,mmolinastudio/backbone,paulfalgout/backbone,liudianpeng/backbone,vincent1988/backbone,Flip120/backbone,ywenjinlin/backbone,liudianpeng/backbone,streamablevideo/backbone,Aplopio/backbone,closeio/backbone,amdjs/backbone,leimd/backbone,wakanpaladin/mybackbone,paulfalgout/backbone,jewsroch/backbone,zhangdimelody/backbone,sunday-star/backbone,au-phiware/backbone,Niades/backbone,lujocom/backbone,Sachin-Ganesh/backbone,wangdahoo/backbone,alekskorolev/lightbones,craigmichaelmartin/backbone,elancom/backbone,sueyeh/backbone,sumyfly/backbone,cailong1028/backbone,aihua/backbone,howtolearntocode/backbone,GrimDerp/backbone,youprofit/backbone,ywenjinlin/backbone,cgvarela/backbone,guahanweb/backbone,dak/backbone,honger05/backbone,guigrpa/backbone,maryrosecook/backbone-df,DannyDelott/backbone,dak/backbone,antoniogarrote/backbone,zhoufan879/backbone,Khan/backbone,moccen/backbone,cailong1028/backbone,howtolearntocode/backbone,gmaclennan/backbone,aihua/backbone,lastjune/backbone,au-phiware/backbone,neocotic/hipbone,closeio/backbone,platinumazure/backbone,vin100bk/backbone,darrrk/backbone,ppker/backbone,yuhualingfeng/backbone,Diwahars/backbone,jordansexton/backboner,jashkenas/backbone,sumyfly/backbone,elancom/backbone,anhtholee/backbone,sueyeh/backbone,rjz/boneless,sitexa/backbone,jashkenas/backbone,ereddate/backbone,webcoding/backbone,moimikey/backbone,jungjung917/backbone,zhoufan879/backbone,elma-cao/backbone,tzkKrbys/backbone,streamablevideo/backbone,zhangdimelody/backbone,moccen/backbone,braddunbar/backbone,Connectlegendary/backbone,jridgewell/backbone,wangcan2014/backbone,Sachin-Ganesh/backbone,kuychaco/backbone,guahanweb/backbone,batigoal1980/backbone_example,chyeh727/backbone,neocotic/hipbone,leimd/backbone,timebackzhou/backbone,tgriesser/backbone,zdespolit/backbone,ThiagoGarciaAlves/backbone,jasoncbautista/backboneX,FormidableLabs/backbone,amitpatange88/backbonejs,ThiagoGarciaAlves/backbone,fanhc019/backbone,moimikey/backbone,Aplopio/backbone,ebsco/backbone,GerHobbelt/backbone,craigmichaelmartin/backbone,nvoron23/backbone,amitpatange88/backbonejs,yawenl/backbone,getshuvo/backbone,vincent1988/backbone,mrblueblue/backbone,virtru-components/backbone,timebackzhou/backbone,FishbaitHarry/backbone,tibic/backbone