#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
const int N = 1e5 + 20, M = 2e5 + 20;
int n, m, fa[N];
bool vis[M];
struct LINE{
    int u, v, id;
}line[M];

int e[M], ne[M], h[M], w[M], idx;
void add(int u, int v, int c){
    e[idx] = v, ne[idx] = h[u], w[idx] = c, h[u] = idx++;
}

bool cmp(LINE x, LINE y){
    return x.id > y.id;
}

int find(int x){
    if(x == fa[x]) return x;
    return fa[x] = find(fa[x]);
}

void slove(){
    sort(line + 1, line + m + 1, cmp);
    for(int i = 1; i <= n; i++) fa[i] = i;
    for(int i = 1; i <= m; i++){
        int u = line[i].u, v = line[i].v, id = line[i].id;
        int fau = find(u), fav = find(v);
        if(fau != fav){
            fa[fau] = fav;
            vis[id] = true;
        }
    }
    int cnt = 0;
    for(int i = 1; i <= m; i++){
        if(!vis[i]) cnt++;
    }
    printf("%d\n", cnt);
    for(int i = 1; i <= m; i++){
        if(!vis[i]) printf("%d ", i);
    }
}

void init(){
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= m; i++){
        vis[i] = false;
        int u, v;
        scanf("%d%d", &u, &v);
        line[i] = {u, v, i};
    }
}

int main(){
    int T = 1;
    scanf("%d", &T);
    while(T--){
        init();
        slove();
    }
    return 0;
}