When running /testforblock on iron bars, fences or panes the result is not as expected.

As can be seen in the attachment, I ran

/testforblock ~1 ~ ~ minecraft:iron_bars east=false

and

/testforblock ~1 ~ ~ minecraft:iron_bars east=true

directed at an iron_bars block with the block state east=true,north=false,west=false,south=false

What I expected to happen was the first command to NOT find the block and the second command to do find the block.

Instead, the opposite happened. The first command resulted in the block being found, despite the block state for "east=" not matching my criteria. The second command resulted in the block not being found, giving the message:
"The block at -144, 67, -125 had the data value of minecraft:iron_bars[east=false,north=false,south=false,west=false] (expected: east=true)"

Note: I was told to make an issue separate from MC-109353 even though both bugs seem similar.

Affected blocks

Last updated for 1.11.2

¹ If the occupied property of the foot part is false, but the head part true

Code analysis

For flower pots, see MC-109353