#include <cstdio>
#include <cstring>
#include <algorithm>
#include <numeric>
#include <vector>
#include <queue>
#include <map>
#include <cmath>
#include <cctype>
#include <set>

namespace uvu
{
#define LOCAL ____________DONT_DEFINE_ME____________
// #define ll long long
// #define inf 0x3f3f3f3f
#define int long long
#define inf 0x3f3f3f3f3f3f3f3fll
#define infll 0x3f3f3f3f3f3f3f3fll
#define debug(...) fprintf(stderr, __VA_ARGS__)
#define gline debug("now is #%d\n", __LINE__)
#define pii std::pair <int, int>
#define mkp std::make_pair
#define fi first
#define se second
char _ST_;
const int BUFSIZE = (1 << 20);
char ibuf[BUFSIZE], *iS = ibuf, *iT = ibuf;
char obuf[BUFSIZE], *oS = obuf, *oT = obuf + BUFSIZE;
char getc()
{
#ifdef LOCAL
	return getchar();
#else
	if(iS == iT) iT = (iS = ibuf) + fread(ibuf, 1, BUFSIZE, stdin);
	return iS == iT ? EOF : *iS++;
#endif
#define getchar ERR
}

void Flush() { fwrite(obuf, 1, oS - obuf, stdout); oS = obuf; }
struct Flusher { ~Flusher(){ Flush(); } }iamflusher;

void putc(char c)
{
#ifdef LOCAL
	putchar(c);
#else
	*oS++ = c;
	if(oS == oT) Flush();
#endif
#define putchar ERR
}

template <typename T = int> T read()
{
	T x = 0, f = 1; char c = getc();
	for(; !isdigit(c); c = getc()) if(c == '-') f = -1;
	for(;  isdigit(c); c = getc()) x = (x << 3) + (x << 1) + (c ^ 48);
	return x * f;
}

template <typename T> void print(T x, char c)
{
static int sta[BUFSIZE], top;
	top = 0;
	if(x < 0) putc('-'), x = -x;
	if(!x) sta[top = 1] = 0;
	for(; x; x /= 10) sta[++top] = x % 10;
	for(; top; ) putc(sta[top--] ^ 48);
	if(c) putc(c);
}

int readstr(char *s, int base)
{
	int idx = base - 1; char c = getc();
	for(; !(isdigit(c) || isalpha(c) || c == '(' || c == '?'); c = getc());
	for(;   isdigit(c) || isalpha(c) || c == '(' || c == '?' ; c = getc()) s[++idx] = c;
	return idx - base + 1;
}

void printf(const char *s) { for(; *s; s++) putc(*s); }
template <typename T, typename ... Args>
void printf(const char *s, T x, Args ... rest)
{
	for(; *s; s++)
	{
		if(*s != '%') { putc(*s); continue; }
		s++; if(*s == 'd') print(x, 0);
		else if(*s == 'c') putc(x);
		printf(s + 1, rest ...);
		return;
	}
}

template <typename T> void ckmax(T &x, T y) { x = x > y ? x : y; }
template <typename T> void ckmin(T &x, T y) { x = x < y ? x : y; }
#define mod 998244353
// #define mod 1000000007
int sm(int x) { return x >= mod ? x - mod : x; }
void plus_(int &x, int y) { x = (x + y >= mod ? x + y - mod : x + y); }
void mul_(int &x, int y) { x = 1ll * x * y % mod; }
int ksm(int a, int b) { int res = 1; for(; b; b >>= 1, mul_(a, a)) if(b & 1) mul_(res, a); return res; }

// 最简单的构造：对于每个点输出以它为根任意一个拓扑序
// 简单的优化：只需要对于每个叶子输出即可
#define N 110
int n, h[N], e[N << 1], ne[N << 1], idx = -1, du[N];
void add_edge(int x, int y) { ne[++idx] = h[x], h[x] = idx, du[e[idx] = y]++; }
void add(int x, int y) { add_edge(x, y), add_edge(y, x); }
std::vector <std::vector <int> > ans;
std::vector <int> now;

void dfs0(int k, int fa)
{
	for(int i = h[k]; ~i; i = ne[i]) if(e[i] != fa) dfs0(e[i], k);
	now.push_back(k);
}

void solve()
{
	// memset(h, idx = -1, sizeof(h));
	n = read(); for(int i = 1; i <= n; i++) h[i] = idx = -1, du[i] = 0;
	ans.clear();
	for(int i = 1; i < n; i++) add(read(), read());
	for(int i = 1; i <= n; i++) if(du[i] == 1) now.clear(), dfs0(i, 0), ans.push_back(now);
	print(ans.size(), '\n');
	for(auto vec : ans) { for(auto t : vec) print(t, ' '); putc('\n'); }
}

void init()
{
	
}

char _ED_;

void mian()
{
	debug("%.3f MB\n", abs(&_ST_ - &_ED_) / 1024.0 / 1024);
	init(); int T = read();
	for(; T; solve(), T--);
}

#ifdef int
	#undef int
#endif
}

int main()
{
	uvu::mian(); return 0;
}