#include <bits/stdc++.h>
using namespace std;
int read(){
    int ret=0,f=1;char ch=getchar();
    while(!isdigit(ch)){if(ch=='-')f=-f;ch=getchar();}
    while( isdigit(ch)){ret=(ret<<3)+(ret<<1)+(ch&15);ch=getchar();}
    return ret*f;
}
int T;
struct node{
    int x,y;
}A1,B1,A2,B2,O1,O2;
int dis(node A,node B){return abs(A.x-B.x)+abs(A.y-B.y);}
long long dis2(node A,node B){return 1ll*(A.x-B.x)*(A.x-B.x)+1ll*(A.y-B.y)*(A.y-B.y);}
double d;
int main(){
    T=read();
    while(T--){
        A1.x=read()*2;A1.y=read()*2;
        B1.x=read()*2;B1.y=read()*2;
        A2.x=read()*2;A2.y=read()*2;
        B2.x=read()*2;B2.y=read()*2;
        O1=(node){(A1.x+B1.x)/2,(A1.y+B1.y)/2};
        O2=(node){(A2.x+B2.x)/2,(A2.y+B2.y)/2};
        d=sqrt(dis2(O2,A2)/2);
        printf("%.10lf\n",dis(O1,O2)/2.0-d);
    }
    return 0;
}