#include <bits/stdc++.h>

using namespace std;

const int N = 505;

inline int read() {
	register int s = 0, f = 1; register char ch = getchar();
	while (!isdigit(ch)) f = (ch == '-' ? -1 : 1), ch = getchar();
	while (isdigit(ch)) s = (s * 10) + (ch & 15), ch = getchar();
	return s * f;
}

inline int readdig() {
	register int s = 0; register char ch = getchar();
	while (!isdigit(ch)) ch = getchar();
	return (ch & 15);
}

vector<int> g[N]; 

int e[N][N], dis[N][N], n;
bool vis[N];

inline void dfs(int now) {
	if (vis[now]) return ;
	vis[now] = 1;
	for (int i : g[now])
		if (!vis[i]) dfs(i);
}

inline void bfs(int now) {
	dis[now][now] = 0;
	queue<int> q; q.push(now);
	while (!q.empty()) {
		int x = q.front();
		q.pop();
		for (int i : g[x])
			if (!dis[now][i] && i != now)
				dis[now][i] = dis[now][x] + 1, q.push(i);
	}
}

int main() {
	int T; cin >> T;
	while (T--) {
		cin >> n; int cnt = 0;
		for (int i = 1; i <= n; ++i)
			for (int j = 1; j <= n; ++j) {
				cnt += e[i][j] = readdig();
				if (e[i][j]) {
					g[i].push_back(j);
					g[j].push_back(i);
				}
			}
		dfs(1);
		for (int i = 1; i <= n; ++i) {
			if (!vis[i]) {
				puts("NO");
				goto fail;
			}
		}
		for (int i = 1; i <= n; ++i) bfs(i);
		for (int i = 1; i <= n; ++i) {
			for (int j = 1; j <= n; ++j)
				if ((dis[i][j] & 1) != e[i][j]) {
					puts("NO");
					goto fail;
				}
		}
		puts("YES");
		cout << cnt / 2 << endl;
		for (int i = 1; i <= n; ++i)
			for (int j = 1; j < i; ++j)
				if (e[i][j]) cout << i << ' ' << j << endl;
		fail:;
		for (int i = 1; i <= n; ++i) {
			g[i].clear(); vis[i] = 0;
			for (int j = 1; j <= n; ++j)
			 e[i][j] = dis[i][j] = 0;
		}
	}
	return 0;
}