// Skyqwq
#include <bits/stdc++.h>

#define pb push_back
#define fi first
#define se second
#define mp make_pair

using namespace std;

typedef long long LL;
typedef pair<int, int> PII;

template <typename T> bool chkMax(T &x, T y) { return (y > x) ? x = y, 1 : 0; }
template <typename T> bool chkMin(T &x, T y) { return (y < x) ? x = y, 1 : 0; }

template <typename T> void inline read(T &x) {
    int f = 1; x = 0; char s = getchar();
    while (s < '0' || s > '9') { if (s == '-') f = -1; s = getchar(); }
    while (s <= '9' && s >= '0') x = x * 10 + (s ^ 48), s = getchar();
    x *= f;
}

const int N = 5e5 + 5, P = 998244353;

int n, m, fa[N], d[N], c[N], deg[N], h[N];

vector<int> g[N];

bool vis[N];

void inline clr() {
	for (int i = 1; i <= n; i++) vis[i] = 0, g[i].clear(), deg[i] = c[i] = 0;
}


void dfs(int u) {
	vis[u] = 1;
	for (int v: g[u]) {
		if (!vis[v]) {
			fa[v] = u;
			d[v] = d[u] + 1;
			dfs(v);
			c[u] += c[v];
		} else if (d[v] < d[u] && fa[u] != v) c[u]++, c[v]--;
	}
}

void inline prework(int n) {
	h[0] = 1;
	h[1] = 1;
	for (int i = 2; i <= n; i++) {
		h[i] = (h[i - 1] + 1ll * (i - 1) * h[i - 2]) % P;
	}
}

void inline work() {
	for (int i = 2; i <= n; i++) {
		if (c[i] > 1) {
			puts("0");
			return;
		}
	}
	
	for (int i = 2; i <= n; i++) {
		if (c[i] == 0) deg[fa[i]]++, deg[i]++;
	}
	int ans = 1;
	for (int i = 1; i <= n; i++)
		ans = 1ll * ans * h[deg[i]] % P;
	printf("%d\n", ans);
}

int main() {
	prework(N - 1);
	int T; read(T);
	while (T--) {
		read(n), read(m);
		for (int i = 1, u, v; i <= m; i++) {
			read(u), read(v);
			g[u].pb(v), g[v].pb(u);
		}
		dfs(1);
		work();
		clr();
	}
    return 0;
}