static void Main(string[] args)
{
using (var prob = new CodeJamProblem('a', ProblemType.Large, 0))
{
int tcase = prob.ReadLineInt32();
for (int cases = 0; cases < tcase; cases++)
{
int[] a = prob.ReadInt32Array();
int r = a[0];
int c = a[1];
string[] ss = prob.ReadLines(r);
char[,] s = new char[r, c];
for (int i = 0; i < r; i++)
{
for (int j = 0; j < c; j++)
{
s[i, j] = ss[i][j];
}
}
bool ok = true;
for (int i = 0; i < r; i++)
{
for (int j = 0; j < c; j++)
{
if (s[i, j] == '#')
{
if (i == r - 1 || j == c - 1)
{
ok = false;
break;
}
if (s[i + 1, j] != '#' || s[i, j + 1] != '#' || s[i + 1, j + 1] != '#')
{
ok = false;
break;
}
s[i, j] = '/';
s[i, j + 1] = '\\';
s[i + 1, j] = '\\';
s[i + 1, j + 1] = '/';
}
if (!ok)
{
break;
}
}
if (!ok)
{
break;
}
}
prob.OutputCase();
if (!ok)
{
prob.WriteLine("Impossible");
}
else
{
for (int i = 0; i < r; i++)
{
string ans = "";
for (int k = 0; k < c; k++)
{
ans += s[i, k];
}
prob.WriteLine(ans);
}
}
}
}
}