#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll mod = 1e9 + 7;
ll fac[200010], inv[200010];
ll qpow(ll a, ll b) {
    ll ret = 1;
    while (b) {
        if (b & 1)ret = ret * a%mod;
        a = a * a%mod; b >>= 1;
    }
    return ret;
}
void init() {
    fac[0] = 1;
    for (int i = 1; i < 200010; i++)fac[i] = fac[i - 1] * i%mod;;
    inv[200010 - 1] = qpow(fac[200010 - 1], mod - 2);
    for (int i = 200010 - 1; i >= 1; i--)inv[i - 1] = inv[i] * i%mod;
}
ll C(int n, int m) {
    return fac[n] * inv[m] % mod*inv[n - m] % mod;
}
int a[200010];
int b[200010];
int c[200010];
int flg[200010];
int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    init();
    int t; cin >> t;
    while (t--) {
        int n; cin >> n;
        int p = 0;
        for (int i = 1; i <= 2 * n; i++)c[i] = flg[i] = 0;
        for (int i = 1; i <= n; i++) {
            int x, y; cin >> x >> y;
            if (x == y)c[x]++;
            else {
                a[++p] = x;
                b[p] = y;
            }
        }

        ll ans = qpow(2,p);
        for (int i = 1; i <= p; i++) {
            if (flg[a[i]] != 2)flg[a[i]] = 1;
            if (flg[b[i]] != 2)flg[b[i]] = 1;
            if (i!=p && b[i] == a[i + 1]) {
                flg[b[i]] = 2;
            }
        }

        for (int i = 1; i <= 2 * n; i++) {

                if (flg[i]==2) {
                    ans *= (C(2 * c[i] + 2, c[i]) + C(2 * c[i] + 2, c[i] + 1))*inv[2]%mod;
                }
                else if (flg[i] == 1) {
                    ans *= C(2 * c[i] + 1, c[i] + 1) % mod;
                }
                else {
                    ans *= C(2 * c[i], c[i]);

                }
                ans %= mod;

        }
        cout << ans << endl;
    }
}