#include<bits/stdc++.h>
using namespace std;
int zs,n,k,js;
int a[210],q[210],dmap[210];
int bi[2]={1,-1};
int main(){
	cin>>zs;
	while(zs--){
		js=1;
		memset(a,0,sizeof(a));
		memset(q,0,sizeof(q));
		memset(dmap,0,sizeof(dmap));
		cin>>n>>k;
		int h=0,t=1;
		for(;t<=k;t++){
			cin>>a[t];
			dmap[a[t]]=1;
			//q[t]=0;
		}
		while(h!=t){
			h++;
			for(int i=0;i<2;i++){
				int dx=bi[i]+a[h];
				if(dx>0&&dx<=n&&!dmap[dx]){
					t++;
					a[t]=dx;
					q[t]=h;
					dmap[dx]=1;
				}
			}
		}
		while(q[t]){
			t=q[t];
			js++;
		}
		cout<<js<<endl;
	}
	return 0;
}