#include <bits/stdc++.h>
#pragma GCC optimize("-O3")
using namespace std;
long long MOD = 1e9 + 7;
long long mpow(long long a, long long b) {
  if (b >= (MOD - 1)) b %= (MOD - 1);
  if (b == 0) return 1;
  long long t1 = mpow(a, b / 2);
  t1 *= t1;
  t1 %= MOD;
  if (b % 2) t1 *= a;
  t1 %= MOD;
  return t1;
}
long long mpow(long long a, long long b, long long p) {
  if (b == 0) return 1;
  long long t1 = mpow(a, b / 2, p);
  t1 *= t1;
  t1 %= p;
  if (b % 2) t1 *= a;
  t1 %= p;
  return t1;
}
long long modinverse(long long a, long long m) {
  long long m0 = m;
  long long y = 0, x = 1;
  if (m == 1) return 0;
  while (a > 1) {
    long long q = a / m;
    long long t = m;
    m = a % m, a = t;
    t = y;
    y = x - q * y;
    x = t;
  }
  if (x < 0) x += m0;
  return x;
}
long long range(long long l, long long r) { return l + rand() % (r - l + 1); }
long long n, m, a, b;
vector<vector<long long> > gr, vis;
void dfs(long long v, long long in) {
  if (in == 0 && v == b) return;
  if (in == 1 && v == a) return;
  vis[v][in] = 1;
  for (long long i = 0; i < ((long long)(gr[v]).size()); i++) {
    if (vis[gr[v][i]][in] == 0) dfs(gr[v][i], in);
  }
}
void solve() {
  cin >> n >> m >> a >> b;
  a--, b--;
  gr.resize(n);
  vis.resize(n, vector<long long>(2, 0));
  for (long long i = 0; i < m; i++) {
    long long t1, t2;
    cin >> t1 >> t2;
    t1--, t2--;
    gr[t1].push_back(t2);
    gr[t2].push_back(t1);
  }
  dfs(a, 0);
  dfs(b, 1);
  long long a1 = 0, a2 = 0;
  for (long long i = 0; i < n; i++)
    if (vis[i][0] == 0) a1++;
  for (long long i = 0; i < n; i++)
    if (vis[i][1] == 0) a2++;
  cout << (a1 - 1) * (a2 - 1) << "\n";
  gr.clear();
  vis.clear();
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long t = 1;
  cin >> t;
  for (long long i = 0; i < t; i++) {
    solve();
  }
  return 0;
}
