What is meant by “Celery Test”?

Simon Sinek mentions about this in his book Start With Why.

When the WHY is communicated clearly by the leader in an organizations it appropriately acts as a FILTER for all decision making even for folks at the lower level based on the clearly stated WHY.

Thus any decision making , hiring , strategies , partnerships , tactics should all be made to pass through the Celery Test and the test would pass only if the WHY stated by the founder percolates right down to the lowest level in the organization to create the desired impact.