Add test plan for compositing and blending
test and fixed #136 and #137
fixed sth
Address review comments from @rhauck and @mibalan
Merge pull request #386 from sherlock917/master

test for #136 and #137, ready for review
Merge pull request #384 from Mire/mbudaes/test_plan_blending

Add test plan for compositing and blending

Thanks Mirela! Looks great.