from math import e


class Combination:

    def __init__(self, MX=10**6, MOD=998244353):
        self.MX = MX
        self.MOD = MOD
        self.fact = [1] * (MX + 1)
        self.inv = [1] * (MX + 1)
        self.f_inv = [1] * (MX + 1)
        for i in range(2, MX + 1):
            self.fact[i] = (self.fact[i - 1] * i) % self.MOD
            self.inv[i] = ( - (self.MOD // i) * (self.inv[self.MOD % i])) % self.MOD
            self.f_inv[i] = (self.f_inv[i - 1] * self.inv[i]) % self.MOD
    
    def invs(self, n):
        if n <= self.MX:
            return self.inv[n]
        else:
            return pow(n, self.MOD - 2, self.MOD)
    
    def p(self, n, r):
        if r > n or r < 0:
            return 0
        return (self.fact[n] * self.f_inv[r]) % self.MOD
    
    def c(self, n, r):
        if r > n or r < 0:
            return 0
        return (self.fact[n] * self.f_inv[r] * self.f_inv[n - r]) % self.MOD

com = Combination()

def solve():

    MOD = 998244353
    N, M = map(int, input().split())
    A = list(map(int, input().split()))
    dic = dict()
    for i in range(N):
        if N - A[i] not in dic:
            dic[N - A[i]] = 0
        dic[N - A[i]] += 1
    ls = list(dic.keys())
    ls.sort()

    lsum = 0
    rsum = 0
    L, R = [], []

    ans = 1
    for i in range(len(ls)):
        now = ls[i]
        j = now - lsum
        k = now - rsum
        if lsum + dic[now] == now:
            L.append(dic[now])
            lsum = now
            if rsum + dic[now] == now and i != len(ls) - 1:
                ans *= 2
                ans %= MOD
        elif rsum + dic[now] == now:
            R.append(dic[now])
            rsum = now
        elif j + k == dic[now] and j > 0 and k > 0:
            lsum = now
            rsum = now
            L.append(j)
            R.append(k)
            ans *= com.c(dic[now], j)
            ans %= MOD
        else:
            print(0)
            return
    ans *= com.c(M, len(L) + len(R))
    ans %= MOD
    print(ans)
    return
        

T = int(input())
for _ in range(T):
    solve()