#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<array<int, 2>> e(m);
        for (auto &[u, v] : e)
            cin >> u >> v;
        vector<int> vis(m), fa(n + 1);
        iota(fa.begin(), fa.end(), 0);
        auto find = [&](auto &find, int x)
        {
            if (x == fa[x])
                return x;
            return fa[x] = find(find, fa[x]);
        };
        for (int i = m - 1; i >= 0; i--)
        {
            auto [u, v] = e[i];
            int fx = find(find, u), fy = find(find, v);
            if (fx == fy)
                vis[i] = 1;
            else
                fa[fx] = fy;
        }
        cout << accumulate(vis.begin(), vis.end(), 0) << '\n';
        for (int i = 0; i < m; i++)
            if (vis[i])
                cout << i + 1 << ' ';
        cout << '\n';
    }
}