#include<bits/stdc++.h>
#define int long long
using namespace std;
const int Max = 1000001;
int t, a[Max], n, Xi[Max], Yi[Max], ans;
signed main() {
	cin>>t;
	while(t--) {
		cin >> n;
		for(int i=1;i<=n;i++) cin>>Xi[i];
		for(int i=1;i<=n;i++) cin>>Yi[i],a[i]=Xi[i]-Yi[i];
		sort(a + 1, a + 1 + n);
		ans = 0;
		int l = 1, r = n;
		while (l < r) {
			while (a[l] + a[r] < 0 && l < r) l++;

			if (a[l] + a[r] >= 0) {
				l++;
				r--;
				ans++;
			}
			if (l == r) break;
		}
		cout << ans << '\n';
	}
	return 0;
}