#include<bits/stdc++.h>
#define MAXN 500005
#define MOD 998244353
#define rint register int
using namespace std;
int Case,N,M,dnt,cactus,ANS;
int dfn[MAXN],lu[MAXN],fa[MAXN],f[MAXN],g[MAXN],h[MAXN];
struct node{int id,odr;bool operator < (const node &rtm) const{return odr<rtm.odr;}
}A[MAXN];
struct Edge{int ent;int to[MAXN*4],nxt[MAXN*4],head[MAXN];void Reset(int n){for(rint i=1;i<=n;i++) head[i]=0; ent=2;}void Adde(int u,int v){to[ent]=v; nxt[ent]=head[u]; head[u]=ent++;}
}E;
void dfs(int u,int dad){dfn[u]=++dnt; fa[u]=dad;for(int e=E.head[u];e;e=E.nxt[e]){int v=E.to[e];if(dfn[v]) continue;dfs(v,u);}
}
void DP(int u,int rt){lu[u]=-1; f[u]=1; int num=0,gson=1;for(int e=E.head[u];e;e=E.nxt[e]){int v=E.to[e];if(lu[v]!=1||v==fa[u]) continue;DP(v,0); num++;gson=1ll*gson*g[v]%MOD;}f[u]=1ll*gson*h[num]%MOD;g[u]=(1ll*f[u]+1ll*gson*h[num-1]%MOD*num)%MOD;
}
int main(){h[0]=h[1]=1;for(int i=1;i<=500000;i++) h[i]=(1ll*h[i-1]+1ll*h[i-2]*(i-1))%MOD;for(scanf("%d",&Case);Case;Case--){scanf("%d%d",&N,&M);E.Reset(N); dnt=0; cactus=1; ANS=1;for(rint i=1;i<=N;i++) lu[i]=dfn[i]=fa[i]=0;for(int i=1,a,b;i<=M;i++)scanf("%d%d",&a,&b),E.Adde(a,b),E.Adde(b,a);dfs(1,0);for(int e=1,u,v;e<=M;e++){u=E.to[e*2]; v=E.to[e*2+1];if(dfn[u]>dfn[v]) swap(u,v);while(v!=u){lu[v]++;if(lu[v]>2){cactus=0;break;}v=fa[v];}}if(!cactus){printf("%d\n",0); continue;}for(int i=1;i<=N;i++) A[i]=(node){i,dfn[i]};sort(A+1,A+N+1);for(int i=1,u;i<=N;i++){u=A[i].id;if(lu[u]==-1) continue;DP(u,1); ANS=1ll*ANS*f[u]%MOD; }printf("%d\n",ANS);}return 0;
}