F

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define pb     push_back
#define _test   int _TEST; cin>>_TEST; while(_TEST--)

int main()
{
    _test
    {
        int n, k;
        cin>>n>>k;

        vector<int> x(k), mark(n);
        for(auto &e: x)     cin>>e;

        for(auto e: x)      mark[e-1] = 1;

        vector<vector<int>> tree(n);

        for(int i=0; i<n-1; i++)
        {
            int u, v;
            cin>>u>>v;

            u--, v--;

            tree[u].pb(v);
            tree[v].pb(u);
        }

        vector<int> lowestMark(n, -1);

        function<void(int, int)> DFS = [&](int u, int p)
        {
            if(mark[u])     lowestMark[u] = 0;

            for(auto v: tree[u])
            {
                if(v == p)      continue;

                DFS(v, u);

                if(lowestMark[v] != -1)
                    lowestMark[u] = max(lowestMark[u], 1+lowestMark[v]);
            }
        };


        DFS(0, -1);

        int ans = 1e9;

        function<void(int, int, int)> DFS2 = [&](int u, int p, int topM)
        {
            multiset<int> mst;
            mst.insert(-1);

            int mmax = max(topM, lowestMark[u]);

            ans = min(ans, max(topM, lowestMark[u]));

            if(mark[u])     mst.insert(0);

            for(auto v: tree[u])
            {
                if(v == p)      continue;

                if(lowestMark[v] != -1)
                    mst.insert(lowestMark[v]+1);
            }

            int tmp;

            for(auto v: tree[u])
            {
                if(v == p)      continue;

                tmp = -1;

                if(topM != -1)      tmp = topM + 1;
                if(mark[u])         tmp = max(tmp, 1);

                if(lowestMark[v] != -1)
                    mst.erase(mst.find(lowestMark[v]+1));

                if(*mst.rbegin() != -1)
                    tmp = max(tmp, *mst.rbegin()+1);

                DFS2(v, u, tmp);

                if(lowestMark[v] != -1)
                    mst.insert(lowestMark[v]+1);
            }
        };

        DFS2(0, -1, -1);

        cout<<ans<<"\n";
    }
}