import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }

struct ModInt(uint M_) {
  import std.conv : to;
  alias M = M_;
  uint x;
  this(ModInt a) { x = a.x; }
  this(uint x_) { x = x_ % M; }
  this(ulong x_) { x = cast(uint)(x_ % M); }
  this(int x_) { x = ((x_ %= cast(int)(M)) < 0) ? (x_ + cast(int)(M)) : x_; }
  this(long x_) { x = cast(uint)(((x_ %= cast(long)(M)) < 0) ? (x_ + cast(long)(M)) : x_); }
  ref ModInt opAssign(T)(inout(T) a) if (is(T == uint) || is(T == ulong) || is(T == int) || is(T == long)) { return this = ModInt(a); }
  ref ModInt opOpAssign(string op, T)(T a) {
    static if (is(T == ModInt)) {
      static if (op == "+") { x = ((x += a.x) >= M) ? (x - M) : x; }
      else static if (op == "-") { x = ((x -= a.x) >= M) ? (x + M) : x; }
      else static if (op == "*") { x = cast(uint)((cast(ulong)(x) * a.x) % M); }
      else static if (op == "/") { this *= a.inv(); }
      else static assert(false);
      return this;
    } else static if (op == "^^") {
      if (a < 0) return this = inv()^^(-a);
      ModInt b = this, c = 1U;
      for (long e = a; e; e >>= 1) { if (e & 1) c *= b; b *= b; }
      return this = c;
    } else {
      return mixin("this " ~ op ~ "= ModInt(a)");
    }
  }
  ModInt inv() const {
    uint a = M, b = x; int y = 0, z = 1;
    for (; b; ) { const q = a / b; const c = a - q * b; a = b; b = c; const w = y - cast(int)(q) * z; y = z; z = w; }
    assert(a == 1); return ModInt(y);
  }
  ModInt opUnary(string op)() const {
    static if (op == "+") { return this; }
    else static if (op == "-") { ModInt a; a.x = x ? (M - x) : 0U; return a; }
    else static assert(false);
  }
  ModInt opBinary(string op, T)(T a) const { return mixin("ModInt(this) " ~ op ~ "= a"); }
  ModInt opBinaryRight(string op, T)(T a) const { return mixin("ModInt(a) " ~ op ~ "= this"); }
  bool opCast(T: bool)() const { return (x != 0U); }
  string toString() const { return x.to!string; }
}

enum MO = 998244353;
alias Mint = ModInt!MO;

enum LIM_INV = 4 * 10^^5 + 10;
Mint[] inv, fac, invFac;
void prepare() {
  inv = new Mint[LIM_INV];
  fac = new Mint[LIM_INV];
  invFac = new Mint[LIM_INV];
  inv[1] = 1;
  foreach (i; 2 .. LIM_INV) {
    inv[i] = -((Mint.M / i) * inv[cast(size_t)(Mint.M % i)]);
  }
  fac[0] = invFac[0] = 1;
  foreach (i; 1 .. LIM_INV) {
    fac[i] = fac[i - 1] * i;
    invFac[i] = invFac[i - 1] * inv[i];
  }
}
Mint binom(long n, long k) {
  if (n < 0) {
    if (k >= 0) {
      return (-1)^^(k & 1) * binom(-n + k - 1, k);
    } else if (n - k >= 0) {
      return (-1)^^((n - k) & 1) * binom(-k - 1, n - k);
    } else {
      return Mint(0);
    }
  } else {
    if (0 <= k && k <= n) {
      assert(n < LIM_INV);
      return fac[cast(size_t)(n)] * invFac[cast(size_t)(k)] * invFac[cast(size_t)(n - k)];
    } else {
      return Mint(0);
    }
  }
}


int N, M;
int[] A;

Mint solve() {
  int L;
  int[] B, C;
  for (int i = 0, j; i < N; i = j) {
    for (j = i; j < N && A[i] == A[j]; ++j) {}
    B ~= A[i];
    C ~= (j - i);
  }
  const K = cast(int)(B.length);
  debug {
    writefln("B = %s, C = %s", B, C);
  }
  
  Mint ans = 1;
  int sumL, sumR;
  auto ls = new int[K];
  auto rs = new int[K];
  foreach_reverse (k; 0 .. K) {
    const l = N - sumL - B[k];
    const r = N - sumR - B[k];
    if (l > 0 && r > 0 && C[k] == l && C[k] == r) {
      if (k != 0) {
        ans *= 2;
      }
      ls[k] = l;
    } else if (l > 0 && r > 0 && C[k] == l + r) {
      ls[k] = l;
      rs[k] = r;
    } else if (l > 0 && C[k] == l) {
      ls[k] = l;
    } else if (r > 0 && C[k] == r) {
      rs[k] = r;
    } else {
      return Mint(0);
    }
    sumL += ls[k];
    sumR += rs[k];
  }
  debug {
    writefln("ls = %s, rs = %s", ls, rs);
  }
  
  {
    int l;
    foreach_reverse (k; 0 .. K) if (ls[k]) {
      if (max(l, N - ls[k] - l) != B[k]) {
        return Mint(0);
      }
      l += ls[k];
    }
  }
  {
    int r;
    foreach_reverse (k; 0 .. K) if (rs[k]) {
      if (max(r, N - rs[k] - r) != B[k]) {
        return Mint(0);
      }
      r += rs[k];
    }
  }
  
  int cnt;
  foreach (k; 0 .. K) {
    if (ls[k]) ++cnt;
    if (rs[k]) ++cnt;
    ans *= binom(C[k], ls[k]);
  }
  ans *= binom(M, cnt);
  return ans;
}

void main() {
  prepare;
  
  try {
    for (; ; ) {
      const numCases = readInt;
      foreach (caseId; 0 .. numCases) {
        N = readInt;
        M = readInt;
        A = new int[N];
        foreach (i; 0 .. N) {
          A[i] = readInt;
        }
        A.sort;
        
        const ans = solve;
        writeln(ans);
      }
    }
  } catch (EOFException e) {
  }
}