t=int(input())
for _ in range(t):
    n=int(input())
    A=list(map(int,input().split()))
    if n==1:
        print(A[0])
        continue
    def check(ans):
        X=[0]*(len(A)+3)
        if len(X)<=ans:
            return False
        for i in A:
            if i>=len(X):
                X[0]+=1
            else:
                X[i]+=1
        d=0
        for i in range(ans,len(X)):
            X[0]+=X[i]
        for i in reversed(range(ans)):
            X[i]-=d
            if X[i]<=0:
                d+=1-X[i]
            else:
                X[0]+=X[i]
        return X[0]>=0
                
                
    ans=0
    for bs in reversed(range(20)):
        ans+=2**bs
        if not check(ans):
            ans-=2**bs
    print(ans)