[INTERNAL] Tree: enhance qunit test
[INTERNAL] Tree: enhance qunit test

Change-Id: I7f7e526ac02a35028777dfda8f491d318d445ba9

SAP/openui5,cschuff/openui5,nzamani/openui5,SAP/openui5,cschuff/openui5,cschuff/openui5,nzamani/openui5,SQCLabs/openui5,SAP/openui5,SQCLabs/openui5,SAP/openui5,nzamani/openui5,SQCLabs/openui5