I'm using testnet and testing my understanding of txn fees and came across a txn that I would not expect a fee to be applied.

From https://en.bitcoin.it/wiki/Transaction_fees

Quote

A transaction will be sent without fees if these conditions are met:
It is smaller than 10 thousand bytes.
All outputs are 0.01 BTC or larger.
Its priority is large enough (see the Technical Info section below)

Using the priority formula in the Technical Info section, I calculated the fees for tx e212c55 using the following information:

Input tx: adff686
Input amt: 399950000
Input age: (Tx e212c55 is in block 68950 - Tx adff686 in block 68414) = 536
Priority = 399950000 x 536 / 225 byte size = 952,769,777.77

This is greater than 57,600,000 priority so why did bitcoind enforce a tx fee of 0.0005? Huh