#pragma GCC optimize(2)
#pragma GCC optimize("Ofast")
#include<map>
#include<set>
#include<cmath>
#include<ctime>
#include<queue>
#include<stack>
#include<cstdio>
#include<vector>
#include<string>
#include<bitset>
#include<numeric>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
using namespace std;
const int MAXN=5e5+10;
const int N=5e5;
const int INF=0x3f3f3f3f;
const long long LINF=0x3f3f3f3f3f3f3f3f;
const int IN_LIMIT=3e7;
static char buf[IN_LIMIT];
static char *pc=buf;
#define getchar() *pc++
inline int read(){
	int num=0;
	char c;
	while((c=getchar())<0x2d);
	do
	{
		num=(num<<1)+(num<<3)+(c^0x30);
	}
	while((c=getchar())>=0x30);
	return num;
}
const int OUT_LIMIT=1e7;
char out[OUT_LIMIT+20],rev[100];
int Len(0);
#define putchar(ch) out[Len++]=ch
#define flush() fwrite(out,1,Len,stdout),Len=0
inline void write(int x){
    int len(0);
    do{
        rev[len++]=(x%10)^0x30;
        x/=10;
    }while(x);
    while(len)
    {
        out[Len++]=rev[--len];
    }
    if(Len>OUT_LIMIT){
        flush();
    }
}
int n,m;
int u[MAXN],v[MAXN];
basic_string <int> pth[MAXN];
basic_string <int> tr[MAXN];
inline void add_edge(int x,int y){
	tr[x].push_back(y);
}
int dfc=0;
int dad[MAXN],dep[MAXN],siz[MAXN];
int son[MAXN],top[MAXN];
int dfn[MAXN],bac[MAXN];
void dfs1(int x){
	dep[x]=dep[dad[x]]+1;
	siz[x]=1;
	son[x]=0;
	for(int to:tr[x])
	{
		if(to^dad[x]){
			dad[to]=x;
			dfs1(to);
			siz[x]+=siz[to];
			if(siz[to]>siz[son[x]]){
				son[x]=to;
			}
		}
	}
}
void dfs2(int x){
	dfc++;
	dfn[x]=dfc;
	bac[dfc]=x;
	if(son[x]){
		top[son[x]]=top[x];
		dfs2(son[x]);
	}
	for(int to:tr[x])
	{
		if(to^dad[x]&&to^son[x]){
			top[to]=to;
			dfs2(to);
		}
	}
}
inline int lca(int x,int y){
	while(top[x]^top[y])
	{
		if(dep[top[x]]<dep[top[y]]){
			swap(x,y);
		}
		x=dad[top[x]];
	}
	if(dep[x]>dep[y]){
		swap(x,y);
	}
	return x;
}
namespace zkw{
	int M;
	int res[MAXN<<2],resp[MAXN<<2],tag[MAXN<<2];
	#define ls(x) (x<<1)
	#define rs(x) (x<<1|1)
	inline void push_up(int x){
		res[x]=max(res[ls(x)],res[rs(x)])+tag[x];
		resp[x]=(res[ls(x)]>=res[rs(x)]?resp[ls(x)]:resp[rs(x)]);
	}
	inline void build(){
		M=1<<(__lg(n)+1);
		memset(res,0,sizeof(int)*(M+M+2));
		memset(resp,0,sizeof(int)*(M+M+2));
		memset(tag,0,sizeof(int)*(M+M+2));
		for(int i=1;i<=n;i++)
		{
			resp[i+M]=i;
		}
		for(int i=M;i;i--)
		{
			push_up(i);
		}
	}
	inline void modify(int l,int r,int v){
		l+=M-1;
		r+=M+1;
		while(l^r^1)
		{
			if(~l&1){
				res[l^1]+=v;
				tag[l^1]+=v;
			}
			if(r&1){
				res[r^1]+=v;
				tag[r^1]+=v;
			}
			l>>=1;
			r>>=1;
			push_up(l);
			push_up(r);
		}
		while(l)
		{
			l>>=1;
			push_up(l);
		}
	}
	inline int qry(){
		return res[1];
	}
	inline int qryp(){
		return resp[1];
	}
}
inline void modify(int x,int y,int v){
	while(top[x]^top[y])
	{
		if(dep[top[x]]<dep[top[y]]){
			swap(x,y);
		}
		zkw::modify(dfn[top[x]],dfn[x],v);
		x=dad[top[x]];
	}
	if(dep[x]>dep[y]){
		swap(x,y);
	}
	zkw::modify(dfn[x],dfn[y],v);
}
int ans[MAXN];
inline void solve(){
	n=read();
	m=read();
	for(int i=1;i<=n;i++)
	{
		tr[i].clear();
	}
	for(int i=1;i<n;i++)
	{
		int x=read(),y=read();
		add_edge(x,y);
		add_edge(y,x);
	}
	dfs1(1);
	top[1]=1;
	dfc=0;
	dfs2(1);
	zkw::build();
	for(int i=1;i<=m;i++)
	{
		u[i]=read();
		v[i]=read();
		modify(u[i],v[i],1);
		pth[lca(u[i],v[i])].push_back(i);
	}
	write(zkw::qry());
	putchar('\n');
	for(int i=1;i<=m;i++)
	{
		int p=bac[zkw::qryp()];
		int x=pth[p].back();
		pth[p].pop_back();
		ans[x]=zkw::qry();
		modify(u[x],v[x],-1);
	}
	for(int i=1;i<=m;i++)
	{
		write(ans[i]);
		putchar(' ');
	}
	putchar('\n');
}
signed main(){
	#ifdef LOCAL
	freopen("data.in","r",stdin);
	freopen("data.out","w",stdout);
	atexit([](){fprintf(stderr,"%.3lfs\n",(double)clock()/CLOCKS_PER_SEC);});
	#endif
	fread(buf,1,IN_LIMIT,stdin);
	read();
	int t=read();
	while(t--)
	{
		solve();
	}
	flush();
	return 0;
}