The Bug:

Test blocks and test instance blocks aren't part of the "#minecraft:dragon_immune" or "#minecraft:wither_immune" tags.

Steps to Reproduce:

1. Place down a test block or a test instance block.
2. Open the F3 debug menu and look at the block.
3. Observe what tags the block has.

Observed Behavior:

Test blocks and test instance blocks aren't part of the "#minecraft:dragon_immune" or "#minecraft:wither_immune" tags.

Expected Behavior:

Test blocks and test instance blocks would be part of the "#minecraft:dragon_immune" and "#minecraft:wither_immune" tags.