#include <stdio.h>
#include <algorithm>
#include <iostream>
#include <map>
#include <stack>
#include <vector>
#include <memory.h>
#include <set>
#include <string.h>
#include <list>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <queue>
#include <time.h>
#define ll long long
#define forn(i,n) for(int i=0;i<n;++i)
#define rep(i,n) for(int i=1;i<=n;++i)
#define repc(i,l,r) for(int i=l;i<=r;++i)
#define mp(a,b) make_pair(a,b)
#define llf long double
#define pii pair<int,int>
using namespace std;
int n, m;
struct Road{
    int x, y, w;
    void read(){
        scanf("%d%d%d", &x, &y, &w);
    }
}rds[300005];
int dsu[300005];
int gp(int u){
    if (!dsu[u]) return u;
    return dsu[u] = gp(dsu[u]);
}
int cnt;
void bind(int u,int v){
    u = gp(u);
    v = gp(v);
    if (u != v){
        --cnt;
        dsu[v] = u;
    }
}
void solve(){
    cin >> n >> m;
    forn(i, m)rds[i].read();
    cnt = n - 1;
    memset(dsu, 0, sizeof(dsu));
    forn(i, m){
        bind(rds[i].x, rds[i].y);
    }
    if (cnt){
        cout << 0 << endl;
        return;
    }
    int nw = 0;
    for (int pos = 30; pos >= 0; --pos){
        cnt = n - 1;
        memset(dsu, 0, sizeof(dsu));
        nw ^= 1 << pos;
        forn(i, m){
            if (!cnt)break;
            if (((rds[i].w&nw)^nw) < (1 << pos)){
                bind(rds[i].x, rds[i].y);
            }
        }
        if (cnt) nw ^= 1 << pos;
    }
    cout << nw << endl;
}
int main(){
//freopen("abc.txt", "r", stdin);
    int T;
    cin >> T;
    while (T--){
        solve();
    }
    return 0;
}