#include<bits/stdc++.h>
using namespace std;
constexpr int N=1000013;
const int P=1e9+7;
typedef long long ll;
int a[N];
void solve() {
    int n;
    cin>>n;
    for(int i=1;i<=n;i++)cin>>a[i];
    if(a[1]){
        cout<<"0\n";
        return;
    }
    for(int i=1;i<=n;i++)if(a[i]>=n) {
        cout<<"0\n";
        return;
    }
    for(int i=1;i<n;i++)if(a[i]>a[i+1]) {
        cout<<"0\n";
        return;
    }
    //[l,r]
    ll k=0,ans=1;
    for(int i=2;i<=n;i++) {
        if(a[i]==a[i-1])ans*=k--,ans%=P;
        else k+=a[i]-a[i-1]-1,ans*=2,ans%=P;
    }
    cout<<ans<<'\n';
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int T=1;cin>>T;
    while(T--)solve();
}