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

const int N = 1005;
vector<int>v[N];
int vis[N];

string ans;
int flag;

void dfs(int cur, int y, string s)
{
    if(cur == y) {
        ans = s;
        flag = 1;
        return;
    }
    
    vis[cur] = 1;

    for(int i = 0 ; i < v[cur].size(); i++)
    {
        int child = v[cur][i];
        if(vis[child] == 0) {
            dfs(child, y, s + to_string(child));
        }
        if(flag == 1) return;
    }
    return;
}

signed main()
{
    int t ; cin >> t;
    while(t--)
    {
        int n, m, x, y;
        cin >> n >> m >> x >> y;
        
        for(int i = 1 ; i <= n; i++) {
            v[i].clear();
            vis[i] = 0;
        }
        
        for(int i = 1 ; i <= m ; i++) {
            int u1, u2;
            cin >> u1 >> u2;
            v[u1].push_back(u2);
            v[u2].push_back(u1);
        }
        
        for(int i = 1 ; i <= n; i++) {
            sort(v[i].begin(), v[i].end());
        }
        
        ans = "";
        flag = 0;
        string s = to_string(x);

        dfs(x, y, s);
        
        for(int i = 0 ; i < ans.size(); i++) {
            cout << ans[i] << " ";
        }
        cout << endl;
        
    }
}