[MC-50768] cannot test for mobs who have 0 health

you cannot test for mobs with 0 health
command to testfor:

testfor @e[type=Skeleton] {HealF:0.0f,CustomName:"FullArmoredDarknut"}

command for the summoned mob:

summon Skeleton ~ ~1 ~ {SkeletonType:1,CustomName:"FullArmoredDarknut",CustomNameVisible:1,Attributes:[{Name:"generic.movementSpeed",Base:0.15},{Name:"generic.attackDamage",Base:1},{Name:"generic.maxHealth",Base:63},{Name:"generic.followRange",Base:30}],Equipment:[{},{id:"minecraft:diamond_boots",Damage:0,Count:1},{id:"minecraft:diamond_leggings",Damage:0,Count:1},{id:"minecraft:diamond_chestplate",Damage:0,Count:1},{id:"minecraft:diamond_helmet",Damage:0,Count:1}],HealF:63.0f,DropChances:[0.0f,0.0f,0.0f,0.0f,0.0f]}

at the moment it is killed, the commandblock still doesn't output
note the commandblock is bound to a comperator timer and outputs this every time:
"FullArmoredDarknut did not match the required data structure"