A test of endurance or patience — a contest to see who can endure or persevere longer.
子どもたちは誰が一番長く氷水に手を入れていられるか根比べをした。
The children had a contest to see who could keep their hand in ice water the longest.
交渉は根比べになり、双方とも譲らなかった。
The negotiations became a test of endurance, and neither side gave in.