#include <iostream>
#include <vector>
using namespace std;

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

    int t;
    cin>>t;
    while(t--)
    {
        int db=0;
        int n,m;
        cin>>n>>m;
        vector<int> state(n+1,0);//1=bolt 2=raktár
        vector<vector<int>>vec(n+1, vector<int>(0, 0));
        for(size_t i  = 0;i<m;i++)
        {
            int u,v;
            cin>>u>>v;
            vec[u].push_back(v);
            vec[v].push_back(u);
        }

        for(int i=1;i<=n;i++)
        {
            int b=0;
            int r=0;
            for(auto j : vec[i])
            {
                if(state[j]==1)
                {
                    b++;
                }
                else if(state[j]==2)
                {
                    r++;
                }
            }
            if(b>r)
            {
                state[i]=2;
                db++;
            }
            if(b<r)
            {
                state[i]=1;
            }
            if(b==r)
            {
                state[i]=2;
                db++;
            }
        }
        cout<<db<<"\n";
        for (size_t i = 1; i <= m; i++)
        {
            if(state[i]==2)
            {
                cout<<i<<" ";
            }
        }
        cout<<"\n";
    }
    
    return 0;
}
/*
2
4 5
1 2
1 3
1 4
2 3
3 4
5 5
1 2
2 3
3 4
4 5
5 1
*/