#include<cstdio>

#include<cstring>

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cmath>

#include<cstdlib>

#include<vector>

#include<queue>

using namespace std;

typedef long long LL;

const int INF=0x3f3f3f3f;

const int maxn=+;

bool vis[maxn];

int b[maxn];

int main()

{

    int T;

    scanf("%d",&T);

    while(T--)

    {

        int n,m,sum=;

        scanf("%d%d",&n,&m);

        memset(vis,,sizeof(vis));

        int x;

        for(int i=; i<=n; ++i)

        {

            scanf("%d",&x);

            if(!x)sum++;

            else vis[x]=;

        }

        b[]=;

        for(int i=; i<=m; ++i)

        {

            if(vis[i])b[i]=b[i-];

            else b[i]=b[i-]+;

        }

        int ans=;

        for(int i=; i<m; ++i)

        {

            int l=i,r=m,mid;

            while(l<=r)

            {

                mid=(l+r)>>;

                if(b[mid]-b[i-]>sum)r=mid-;

                else l=mid+;

            }

            mid=(l+r)>>;

            ans=max(ans,mid-i+);

        }

        printf("%d\n",ans);

    }

    return ;

}