#include<cstdio>
#include<algorithm>
#define mod 1000000007
using namespace std;
int T,inv4,n,x,y,ans;
typedef long long ll;
int ksm(int x,int y)
{
    int ans=1;
    while (y)
    {
        if (y&1) ans=(ll)ans*x%mod;
        x=(ll)x*x%mod;
        y>>=1;
    }
    return ans;
}
int main()
{
    inv4=ksm(4,mod-2);
    scanf("%d",&T);
    while (T--)
    {
        scanf("%d",&n);
        scanf("%d",&x);
        ans=x/2;
        for (int i=2;i<=n;i++)
        {
            scanf("%d",&y);
            ans=(ans+(ll)(y-x)*inv4%mod)%mod;
            x=y;
        }
        printf("%d\n",ans);
    }
}