#include <bits/stdc++.h>
using namespace std;
#define maxn 1000000
#define mod 998244353
#define int long long
int n, m, dep[maxn], g[maxn];
int timer, dfn[maxn], f[maxn];
int fa[maxn], mark[maxn], tot;
int cnt, ans;struct edge
{int cnp, head[maxn], to[maxn], last[maxn];edge() { cnp = 1; }void add(int u, int v){to[cnp] = v, last[cnp] = head[u], head[u] = cnp ++;to[cnp] = u, last[cnp] = head[v], head[v] = cnp ++;}
}E1;struct node
{int id, dep;
}a[maxn];bool cmp(node a, node b) { return a.dep < b.dep; }int read()
{int x = 0, k = 1;char c;c = getchar();while(c < '0' || c > '9') { if(c == '-') k = -1; c = getchar(); }while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();return x * k;
}void pre()
{g[0] = g[1] = 1;for(int i = 2; i < maxn; ++ i) g[i] = (g[i - 1] + (i - 1)*g[i - 2]) % mod;return;
}void Tarjan(int u)
{dfn[u] = ++ timer;for(int i = E1.head[u]; i; i = E1.last[i]){int v = E1.to[i]; if(dfn[v]) continue;fa[v] = u; dep[v] = dep[u] + 1; Tarjan(v);}return;
}void dfs(int u, int rt)
{mark[u] = -1; f[u] = 1; int tot = 0;for(int i = E1.head[u]; i; i = E1.last[i]){int v = E1.to[i]; if(v == fa[u] || mark[v] != 1) continue;tot ++; dfs(v, 0); f[u] = f[u] * f[v] % mod;}if(!rt) f[u] = f[u] * g[tot + 1] % mod;else f[u] = f[u] * g[tot] % mod;return;
}void Work()
{n = read(), m = read(); E1.cnp = 2;for(int i = 1; i <= n; i ++) mark[i] = fa[i] = dep[i] = dfn[i] = E1.head[i] = 0;for(int i = 1; i <= m; i ++){int u = read(), v = read();E1.add(u, v);}dep[1] = 1; Tarjan(1);for(int i = 1; i <= m; i ++){int u = E1.to[i << 1], v = E1.to[i << 1 | 1];if(dfn[u] < dfn[v]) swap(u, v);while(u != v) {if(mark[u] == 2) { printf("0\n"); return; }mark[u] ++; u = fa[u];}}for(int i = 1; i <= n; i ++) a[i].id = i, a[i].dep = dep[i];sort(a + 1, a + n + 1, cmp); ans = 1;for(int i = 1; i <= n; i ++){int x = a[i].id; if(mark[x] == -1) continue;dfs(x, 1); ans = ans * f[x] % mod;}printf("%lld\n", ans); return;
}signed main()
{pre(); int T = read();while(T --) Work();return 0;
}