if fn() {
			return true
		}
		if time.Until(deadline) < pollDuration {
			return false
		}
		time.Sleep(pollDuration)
	}
}

// waitForFree checks db.numFreeConns until either it equals want or
// the maxWait time elapses.
func waitForFree(t *testing.T, db *DB, want int) {
	var numFree int
	if !waitCondition(t, func() bool {
		numFree = db.numFreeConns()
		return numFree == want
	}) {