#include<bits/stdc++.h>
using namespace std;
int T,n,a,b,P=1e9+7,ans;
int qp(int x,int y)
{
    int r=1;
    for(;y;y/=2,x=1ll*x*x%P)if(y&1)r=1ll*r*x%P;
    return r;
}
main()
{
    cin>>T;
    while(T--)
    {
        cin>>n>>a;n--;ans=a/2;
        if(n)
        {
            while(n--)cin>>b;
            ans=(1ll*(b-a)*qp(4,P-2)+ans)%P;
        }
        cout<<ans<<endl;
    }
}