from heapq import heappush,heappop,heapify
from collections import deque,defaultdict,Counter
import itertools
from itertools import permutations,combinations
import sys
import bisect
import string
import math
import time
#import random
def I():
    return int(input())
def MI():
    return map(int,input().split())
def LI():
    return [int(i) for i in input().split()]
def LI_():
    return [int(i)-1 for i in input().split()]
def StoI():
    return [ord(i)-97 for i in input()]
def ItoS(nn):
    return chr(nn+97)
def GI(V,E,Directed=False,index=0):
    org_inp=[]
    g=[[] for i in range(n)]
    for i in range(E):
        inp=LI()
        org_inp.append(inp)
        if index==0:
            inp[0]-=1
            inp[1]-=1
        if len(inp)==2:
            a,b=inp
            g[a].append(b)
            if not Directed:
                g[b].append(a)
        elif len(inp)==3:
            a,b,c=inp
            aa=(inp[0],inp[2])
            bb=(inp[1],inp[2])
            g[a].append(bb)
            if not Directed:
                g[b].append(aa)
    return g,org_inp
def show(*inp,end='\n'):
    if show_flg:
        print(*inp,end=end)
YN=['Yes','No']
mo=10**9+7
inf=float('inf')
l_alp=string.ascii_lowercase
u_alp=string.ascii_uppercase

#sys.setrecursionlimit(10**5)
input=lambda: sys.stdin.readline().rstrip()

show_flg=False
show_flg=True

t=I()
for _ in range(t):
    n,m,a,b=LI()
    a,b=a-1,b-1
    ans=0
    
    g,c=GI(n,m)
    
    vb=[1 for i in range(n)]
    va=[1 for i in range(n)]
    
    q=[b]
    while q:
        c=q.pop()
        vb[c]=0
        for nb in g[c]:
            if vb[nb]==1 and nb!=a:
                q.append(nb)
                vb[nb]=0
                
    q=[a]
    while q:
        c=q.pop()
        va[c]=0
        for nb in g[c]:
            if va[nb]==1 and nb!=b:
                q.append(nb)
                va[nb]=0
         
    x,y=sum(vb),sum(va)       
    
    ans=(x-1)*(y-1)
    print(ans)
    
    