#include "bits/stdc++.h"
using namespace std;
#define int long long
#define pb push_back
#define mp make_pair
#define vi vector<int>
#define vb vector<bool>
#define pii pair<int,int>
#define mii map<int,int>
#define all(c)  c.begin(), c.end()
#define rall(c) c.rbegin(), c.rend()
#define tr(container, it) for(typeof(container.begin()) it = container.begin(); it != container.end(); it++)
#define gcd(a,b) __gcd(a,b)
#define lcm(a,b)  (x/gcd(x,y))*y
#define inf (long long) 1e18
#define neg_inf (long long) (-1*1e18)
#define F first
#define S second
#define sz(x) ((int)(x).size())
#define rep(i,n)  for(int i=0;i<n;i++)
#define repd(i,n) for(int i=n-1;i>=0;i--)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define deb(x) cout << #x << "=" << x <<"\n";
const int N = 1e9 + 7;

int pow(int x, int y) { int res = 1; while (y > 0) { if (y & 1) res = ((res) * (x)); res %= N; y = y >> 1; x = ((x) * (x)); } return res; }
int pow(int x, int y, int p)  {  int res = 1; x = x % p; while (y > 0) {if (y & 1) res = (res * x) % p; y = y >> 1; x = (x * x) % p;}   return res; }


unsigned long long power(unsigned long long x,
                         int y, int p)
{
    unsigned long long res = 1; // Initialize result

    x = x % p; // Update x if it is more than or

    while (y > 0) {
        if (y & 1)
            res = (res * x) % p;
          y = y >> 1; // y = y/2
        x = (x * x) % p;
    }
    return res;
}

unsigned long long modInverse(unsigned long long n, int p)
{
    return power(n, p - 2, p);
}
unsigned long long nCrModPFermat(unsigned long long n,
                                 int r, int p)
{
    if (r == 0)
        return 1;
    unsigned long long fac[n + 1];
    fac[0] = 1;
    for (int i = 1; i <= n; i++)
        fac[i] = (fac[i - 1] * i) % p;

    return (fac[n] * modInverse(fac[r], p) % p * modInverse(fac[n - r], p) % p) % p;
}


void solve()
{
    int n,m;
    cin>>n>>m;
    map<int,int> mm;
    rep(i,n-1)
    {
        int a;
        cin>>a;
        mm[a]++;
    }
    mm[0]=1;
    int srk=0;
    if(sz(mm)==(*mm.rbegin()).F+1)
    {
        vector<int> kk;
        for(auto x:mm)
        {
            kk.pb(x.S);
        }
        int ans=1;
        for(int i=1;i<sz(kk);i++)
        {
            srk+=(kk[i]*(kk[i]-1))/2;
            srk%=N;
            ans*=pow(kk[i-1],kk[i],N);
            ans%=N;
        }

        if(srk>=(m-(n-1)))
            ans*=nCrModPFermat(srk,m-(n-1),N);
        else
        {
            cout<<0<<"\n";
            return;
        }
        ans%=N;
        cout<<ans<<"\n";
    }
    else
    {
        cout<<0<<"\n";
    }
}



int32_t main()
{
  // #ifndef ONLINE_JUDGE
 //    freopen("gymnastics.in", "r", stdin);
 //    freopen("gymnastics.out", "w", stdout);
  // #endif
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    int t=1;
    cin>>t;

   while(t--)
   {
      solve();
   }
}






//code by-Roshan











//unnecessary
// bool cmp(pair<int,int> &a,pair<int,int> &b)
// {
//  if(a.F==b.F)
//    return (a.S<b.S);
//  else
//    return (a.F<b.F);
//  //< =chota wala pehle
//  //> =chota wala baad me
// }


//better use this structure
// struct s{
//  int a;
//  bool operator <(const s &x) const
//  {
//    return (a>x.a);
//  }
// };



//  priority_queue<int,vector<int>,greater<>> p;
// (priority queue as min heap)


//important to use this one
// cout<<fixed<<setprecision(3)<<x<<" ";