Minecraft 1.12 testfor command conversion to 1.13

I was using the /testfor command to have a command block open an iron door if there was a feather (or other item) in a nearby item frame. 1.13 doesn't seem to recognize it. Anybody know how this works in 1.13?

testfor @e[type=Item_Frame,r=5] {Item:{id:"minecraft:feather"}}

The /testfor command became obsolete in Minecraft 1.13, and has been replaced by the /execute command^*.

Quoting user RecycledCap:

nbt data is a selector in the new update so you can do for example
execute at @e[nbt={<nbt>}]

You can do this to fix your problem:

/execute if entity @p[nbt={SelectedItem:{id:"<item>":}}] run <command>

It will do the same as typing /testfor @e {SelectedItem:{id:"<item>"}} and then putting a comparator to the command block with the command, and then running the command which you wanna run.

In your case,
testfor @e[type=Item_Frame,r=5] {Item:{id:"minecraft:feather"}}
becomes something like
/execute if entity @e[type=Item_Frame,r=5;nbt={SelectedItem:{id:"minecraft:feather":}}] run <command>.

^{* Source is this thread on Minecraftforum.net}

Joachim is close but the command will not succeed.

The testfor command has been removed and was replaced with the if option in the execute command.

The execute command equivalent:

execute if entity @e[type=minecraft:item_frame,distance=..5,nbt={Item:{id:"minecraft:feather"}}] run <chained command>

Replace chained command with whatever command you want to execute if the conditions are true.