#include<bits/stdc++.h>
#define N 500107
#define M N<<2|1
#define mo 998244353
#define LL long long
using namespace std;
LL h[N]; int n,T,a,b,m;
void pre() {h[0]=1;for (int i=1;i<N;i++) h[i]=(h[i-1]+(i>1?h[i-2]*(i-1):0))%mo;
}
#define sight(c) ('0'<=c&&c<='9')
inline void read(int &x){static char c;for (c=getchar();!sight(c);c=getchar());for (x=0;sight(c);c=getchar())x=x*10+c-48;
}
void write(int x){if (x<10) {putchar('0'+x); return;} write(x/10); putchar('0'+x%10);}
inline void writeln(int x){ if (x<0) putchar('-'),x*=-1; write(x); putchar('\n'); }
inline void writel(int x){ if (x<0) putchar('-'),x*=-1; write(x); putchar(' '); }
struct Node{#define eho(x) for(int i=head[x];i;i=net[i])#define v fall[i]LL ans,f[N],g[N];int s[N],top,tim,tot,vis[N],low[N],dfn[N],head[N],net[M],fall[M],catus,col[N];void clear(int n) { n=min(sizeof vis,(3+n)*(sizeof top));ans=1; memset(vis,0,n); top=0; tim=0;tot=1; memset(head,0,n); memset(col,0,n);memset(dfn,0,n),memset(low,0,n); catus=0;}void init() {ans=1; memset(vis,0,sizeof vis); top=0; tim=0;tot=1; memset(head,0,sizeof head); memset(col,0,sizeof col);memset(dfn,0,sizeof dfn),memset(low,0,sizeof low); catus=0;}inline void add(int x,int y){fall[++tot]=y; net[tot]=head[x]; head[x]=tot;}inline void adds(int x,int y) {add(x,y); add(y,x);}void Tarjan(int x,int fa){dfn[x]=low[x]=++tim;s[++top]=x;bool flag=0;eho(x) if (v!=fa) {if (!dfn[v])  { Tarjan(v,x); low[x]=min(low[x],low[v]);if (low[v]<dfn[x]) {if (flag) {catus=1;return;}flag|=1;}} else {low[x]=min(low[x],dfn[v]);if (dfn[v]<dfn[x]) {if (flag) {catus=1;return;}flag|=1;    }}}if (dfn[x]==low[x]) do col[s[top--]]=x; while (s[top+1]!=x);}void dfs(int x,int fa){vis[x]=1;f[x]=1; g[x]=0;int num=0;eho(x) {if (col[x]==col[v]||fa==v) continue;dfs(v,x);f[x]=f[x]*g[v]%mo;num++;}g[x]=f[x]*h[num]%mo+f[x]*h[num-1]%mo*num%mo;f[x]=f[x]*h[num]%mo;}inline LL work() {Tarjan(1,0);if (catus) return 0;for (int i=1;i<=n;i++) if (!vis[i]) {dfs(i,0); ans=ans*f[i]%mo;} return ans;}
}G;int NN;
signed main () {freopen("a.in","r",stdin);freopen("a.out","w",stdout);read(T); pre(); G.init();while (T--) {read(n); read(m); //NN=max(n,m);while (m--) read(a),read(b),G.adds(a,b);writeln(G.work());G.clear(n);} return 0;
}