#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
const int N = 1e6 + 20, M = 2e6 + 20;
int n, m;
bool vis[N], vis_line[M];
vector<int> ans;
struct LINE{
    int a, b;
}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++;
}

void dfs(int u, int form){
    for(int i = h[u]; ~i; i = ne[i]){
        int v = e[i], c = w[i];
        if(c == form || vis_line[c]) continue;
        if(vis[v]) ans.push_back(c);
        vis_line[c] = true;
        vis[v] = true;
        dfs(v, c);
    }
}

void slove(){
    for(int i = 1; i <= m; i++){
        int a = line[i].a, b = line[i].b;
        if(!vis[a]){
            vis[a] = true;
            dfs(a, i);
        }
    }
    sort(ans.begin(), ans.end());
    printf("%d\n", (int)ans.size());
    for(auto it: ans){
        printf("%d ", it);
    }
    printf("\n");
}

void init(){
    ans.clear();
    memset(h, -1, sizeof h);
    memset(vis, 0, sizeof vis);
    memset(vis_line, 0, sizeof vis_line);
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= m; i++){
        int a, b;
        scanf("%d%d", &a, &b);
//         if(a == b){
//             ans.push_back(i);
//         }
        add(a, b, i);
        add(b, a, i);
        line[i] = {a, b};
    }
}

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