#pragma comment(linker, "/STACK:102400000,102400000")

#include<cstdio>
#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<cstring>
using namespace std;

typedef long long LL;
typedef vector<int> VI;

#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define EACH(i,c) for(__typeof((c).begin()) i=(c).begin(),i##_end=(c).end();i!=i##_end;++i)
#define eprintf(s...)  fprintf(stderr, s)

template<class T> inline void amin(T &x, const T &y) { if (y<x) x=y; }
template<class T> inline void amax(T &x, const T &y) { if (x<y) x=y; }

const LL INF = 1ll<<55;

int T;
int N, K;
VI G[50111];
int La[50111], Lb[50111];
LL mi[50111], ma[50111];
LL mid;

VI ord;
int par[50111];

//void dfs(int v, int p) {
//    EACH (e, G[v]) if (*e != p) {
//    amax(mi[*e], mi[v] - mid);
//    amin(ma[*e], ma[v] + mid);
//    dfs(*e, v);
//    amax(mi[v], mi[*e] - mid);
//    amin(ma[v], ma[*e] + mid);
//    }
//}

bool ok() {
    REP (i, N) {
    mi[i] = -INF;
    ma[i] = INF;
    }
    REP (i, K) {
    int v = La[i];
    amax(mi[v], (LL)Lb[i]);
    amin(ma[v], (LL)Lb[i]);
    }

    REP (i, N) {
    int v = ord[N-1-i];
    EACH (e, G[v]) if (*e != par[v]) {
        amax(mi[v], mi[*e] - mid);
        amin(ma[v], ma[*e] + mid);
    }
    }
    REP (i, N) {
    int v = ord[i];
    EACH (e, G[v]) if (*e != par[v]) {
        amax(mi[*e], mi[v] - mid);
        amin(ma[*e], ma[v] + mid);
    }
    }
    REP (i, N) if (ma[i] < mi[i]) return false;
    return true;
}

void MAIN() {
    scanf("%d%d", &N, &K);
    REP (i, N) {
    G[i].clear();
    }
    REP (i, N-1) {
    int x, y;
    scanf("%d%d", &x, &y);
    x--; y--;
    G[x].push_back(y);
    G[y].push_back(x);
    }
    REP (i, K) {
    scanf("%d%d", La+i, Lb+i);
    La[i]--;
    }

    REP (i, N) par[i] = -1;
    ord.clear(); ord.reserve(N); ord.push_back(0);
    REP (i, N) {
    int v = ord[i];
    EACH (e, G[v]) if (*e != par[v]) {
        par[*e] = v;
        ord.push_back(*e);
    }
    }


    LL lo = -1, hi = 1000000000;
    while (hi - lo > 1) {
    mid = (lo + hi) / 2;
    (ok()? hi: lo) = mid;
    }
    printf("%d\n", (int)hi);
}

int main() {
    scanf("%d", &T);
    REP (i, T) MAIN();


    return 0;
}