#pragma comment(linker, "/STACK:102400000,102400000")
#include<queue>
#include<stdio.h>
#include<string.h>
#include<algorithm>
#define N 110000
using namespace std;
typedef long long ll;
int n,next[N<<1],to[N<<1],head[N],ce;
int du[N];
ll L[N],R[N];
int v[N];
queue<int>q;
bool yezi[N];
void add(int x,int y)
{
    to[++ce]=y;
    next[ce]=head[x];
    head[x]=ce;
}
bool judge(int mid)
{
    memset(du,0,sizeof(int)*(n+1));
    memset(L,0,sizeof(ll)*(n+1));
    memset(R,0x3f,sizeof(ll)*(n+1));
    int i,x,cnt=0;
    for(i=1;i<=ce;i++)
        du[to[i]]++;
    while(!q.empty())    q.pop();
    for(i=1;i<=n;i++)
        if(du[i]==1)
        {
            q.push(i);
            if(v[i]!=0)
                L[i]=v[i],R[i]=v[i];
        }
    while(!q.empty())
    {
        x=q.front(),q.pop();
        L[x]=max(L[x],1ll);
        if(L[x]>R[x])
            return 0;
        for(i=head[x];i;i=next[i])
        {
            if(du[to[i]]>=1&&!yezi[to[i]])
            {
                ll l=L[x]-mid,r=R[x]+mid;
                L[to[i]]=max(L[to[i]],l);
                R[to[i]]=min(R[to[i]],r);
                du[to[i]]--;
                if(du[to[i]]<=1)
                    q.push(to[i]);
            }
        }
    }
    return 1;
}
int main()
{
    int c,T,m,i,j,k,x,y;
    int l,r,mid;
    scanf("%d",&T);
    for(c=1;c<=T;c++)
    {
        scanf("%d%d",&n,&m);
        memset(v,0,sizeof(int)*(n+1));
        memset(du,0,sizeof(int)*(n+1));
        memset(yezi,0,sizeof(bool)*(n+1));
        memset(head,0,sizeof(int)*(n+1));
        ce=0;
        for(i=1;i<n;i++)
        {
            scanf("%d%d",&x,&y);
            add(x,y),add(y,x);
            du[x]++,du[y]++;
        }
        for(i=1;i<=m;i++)
        {
            scanf("%d%d",&x,&y);
            v[x]=y;
        }
        for(i=1;i<=n;i++)
            if(du[i]==1)
                yezi[i]=1;
        if(n==2)
        {
            if(m==2)
                printf("%d\n",abs(v[1]-v[2]));
            else
                printf("0\n");
            continue;
        }
        l=0,r=1e9;
        while(l<=r)
        {
            mid=l+r>>1;
            if(judge(mid))
                r=mid-1;
            else
                l=mid+1;
        }
        printf("%d\n",l);
    }
    return 0;
}