#include <bits/stdc++.h>
using namespace std;

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int t;
    cin >> t;
    while (t--)
    {
        int n, m;
        cin >> n >> m;
        vector<vector<pair<int, int>>> adj(n + 1);
        for (int i = 1, u, v; i <= m; i++)
        {
            cin >> u >> v;
            adj[u].push_back({v, i});
            adj[v].push_back({u, i});
        }
        for (int i = 1; i <= n; i++)
            sort(adj[i].begin(), adj[i].end(), [&](auto &e1, auto &e2)
                 { return e1.second > e2.second; });
        vector<int> vis(n + 1);
        vector<int> ans;
        vector<pair<int, int>> tmp;
        auto add = [&](int x, int y)
        { tmp.push_back({x, y}); };
        auto del = [&]()
        { tmp.pop_back(); };
        auto dfs = [&](auto &dfs, int cur, int id) -> void
        {
            vis[cur] = 1;
            for (auto [i, v] : adj[cur])
            {
                if (v == id)
                    continue;
                if (vis[i])
                {
                    int mi = v;
                    if (!tmp.empty())
                    {
                        auto it = prev(tmp.end());
                        while (it->second != i)
                        {
                            mi = min(mi, it->first);
                            if (it != tmp.begin())
                                it--;
                            else
                                break;
                        }
                    }
                    ans.push_back(v);
                }
                else
                {
                    add(v, cur);
                    dfs(dfs, i, v);
                    del();
                }
            }
        };
        for (int i = 1; i <= n; i++)
            if (!vis[i])
                dfs(dfs, i, -1);
        sort(ans.begin(), ans.end());
        ans.erase(unique(ans.begin(), ans.end()), ans.end());
        cout << ans.size() << '\n';
        for (int i : ans)
            cout << i << ' ';
        cout << '\n';
    }
}