#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>

using namespace std;

#define mymin(x,y) ((x)<(y)?(x):(y))
#define mymax(x,y) ((x)>(y)?(x):(y))
struct edge{
    int t,nxt;
}a[100009];
int T,n,k;
int cur,fir[50009],now[50009],s[50009],t[50009],cnt,x,y,l,r;
int lp[50009],rp[50009],v[50009];
bool vis[50009];
queue <int> q;
void addedge(int from,int to){
    cur++;
    if (fir[from]==0) fir[from]=cur;
    a[cur].t=to;
    a[now[from]].nxt=cur;
    now[from]=cur;
}
void init(){
    memset(fir,0,sizeof(fir[0])*(n+5));
    memset(now,0,sizeof(now[0])*(n+5));
    memset(a,0,sizeof(a[0])*(cur+5));
    memset(vis,0,sizeof(vis[0])*(n+5));
    memset(s,0,sizeof(s[0])*(n+5));
    memset(t,0,sizeof(t[0])*(n+5));
    memset(v,0,sizeof(v[0])*(n+5));
    cur=cnt=0;
}
void bfs(){
    q.push(1);
    vis[1]=1;
    s[++cnt]=1;
    t[1]=1;
    while(!q.empty()){
        int x=q.front();
        q.pop();
        for (int i=fir[x];i;i=a[i].nxt){
            if (vis[a[i].t]) continue;
            s[++cnt]=a[i].t;
            q.push(a[i].t);
            vis[a[i].t]=1;
            t[a[i].t]=cnt;
        }
    }
}
bool chk(int lim){
    memset(lp,0,sizeof(lp[0])*(n+5));
    memset(rp,0,sizeof(rp[0])*(n+5));
    for (int xx=n;xx>=1;xx--){
        int cur=s[xx];
        lp[cur]=1,rp[cur]=1000000000;
        if (!v[cur]){
            for (int i=fir[cur];i;i=a[i].nxt){
                if (t[a[i].t]<t[cur]) continue;
                lp[cur]=mymax(lp[cur],lp[a[i].t]-lim);
                rp[cur]=mymin(rp[cur],rp[a[i].t]+lim);
                if (rp[cur]<lp[cur]) return false;
            }
        }
        else{
            lp[cur]=rp[cur]=v[cur];
            for (int i=fir[cur];i;i=a[i].nxt){
                if (t[a[i].t]<t[cur]) continue;
                if (lp[a[i].t]-lim>v[cur] || rp[a[i].t]+lim<v[cur]) return false;    
            }
        }
    }
    return true;
}
int main(){
#ifdef YJQ_LOCAL
    freopen(".in","r",stdin);
#endif
    scanf("%d",&T);
    while(T--){
        init();
        scanf("%d%d",&n,&k);
        for (int i=1;i<n;i++){
            scanf("%d%d",&x,&y);
            addedge(x,y);
            addedge(y,x);
        }
        while(k--){
            scanf("%d%d",&x,&y);
            v[x]=y;
        }
        bfs();
        l=0,r=1000000000;
        while(r-l>1){
            int mid=(l+r)>>1;
            if (chk(mid)) r=mid;
            else l=mid;
        }
        if (chk(l)) printf("%d\n",l);
        else printf("%d\n",r);
    }
}