Better testing for branches on L1103 and L1396 of modulargcd.py

Maybe it worth setting random.seed() instead, but I can't
figure yet how to play nicely with caching.

diofant/polys/tests/test_modulargcd.py

@@ -328,6 +328,14 @@ def test_modgcd_algebraic_field():
     assert func_field_modgcd(f, g) == (A.one, f, g)
 
 
+def test_modgcd_algebraic_field_random():
+    A = QQ.algebraic_field(sqrt(2), sqrt(3))
+    R, x, y, z = ring("x, y, z", A)
+    h = x**2*y**3 + 1111*sqrt(6)/12*z
+    f, g = h*(11*y**3 + 2), h**2*(y + x - 1)
+    assert func_field_modgcd(f, g) == (h, 11*y**3 + 2, h*(y + x - 1))
+
+
 # when func_field_modgcd suppors function fields, this test can be changed
 def test_modgcd_func_field():
     D, t = ring("t", ZZ)