Originally Posted by dddd

For your test purposes, you can simply engage the two ends of your chain with the chainring, leaving a 2-link gap that is toward the front of the bicycle. The free ends can be held in place with nothing more than a loop of wire, string or a twist-tie and will not fall out of place on the chainring unless the chainring is rotated.
You'll have to do all of your "shifting" by hand, moving the thankfully-clean chain to the cogs/rings that are to be evaluated for chain "tension".
But doing it your way (with a re-installed pair of links) is also fine, for testing, just not for any serious riding to follow.