#include <bits/stdc++.h>   using namespace std;   int main() {     long long int t;     cin >> t;     while (t--) {       long long int n;       cin >> n;       long long int a[n];       long long int sum = 0;       for (int i = 0; i < n; i++) {         cin >> a[i];         if (!(i & 1)) sum += a[i];       }       long long int best = 0;       long long int cur = 0;       long long int z, z1;       if (n & 1)         z = n - 1;       else         z = n;       for (int i = 0; i < z; i += 2) {         cur = max(0ll, cur + a[i + 1] - a[i]);         best = max(cur, best);       }       cur = 0;       if (!(n & 1))         z1 = n - 1;       else         z1 = n;       for (int i = 1; i < z1; i += 2) {         cur = max(0ll, cur + a[i] - a[i + 1]);         best = max(cur, best);       }       cout << sum + best << endl;     }   }   