Playing Cornish club, partner opens 1C, showing 2+ cards (you open this with all 11-15 balanced hands). After the double, your partner insists that 1S is not forcing despite your best efforts to convince him otherwise, and duly passes it (2C would be a GF relay starter, so according to partner all other calls are not forcing). RHO jumps a few levels to 5D, apparently showing a good hand.
Your call? Objections to the published methods are duly noted. Partner would usually have exactly 3 spades to pass 1S here. If you want to make it more realistic, assume partner responded 1NT showing 11+-15.