Mark test as random to avoid failure

Author: user202729

src/sage/rings/number_field/number_field.py

@@ -8780,30 +8780,30 @@ def subfields(self, degree=0, name=None):
         polynomials are supported (:issue:`252`)::
 
             sage: K.<a> = NumberField(2*x^4 + 6*x^2 + 1/2)
-            sage: sorted(K.subfields(), key=lambda x: x[0].discriminant())
-            [(Number Field in a3 with defining polynomial x^2 + 2,
+            sage: l = K.subfields(); l  # random (see :issue:`39153`)
+            [(Number Field in a0 with defining polynomial x,
               Ring morphism:
-                From: Number Field in a3 with defining polynomial x^2 + 2
+                From: Number Field in a0 with defining polynomial x
                 To:   Number Field in a with defining polynomial 2*x^4 + 6*x^2 + 1/2
-                Defn: a3 |--> 2*a^3 + 5*a,
+                Defn: 0 |--> 0,
               None),
-             (Number Field in a2 with defining polynomial x^2 + 4,
+             (Number Field in a1 with defining polynomial x^2 - 2,
               Ring morphism:
-                From: Number Field in a2 with defining polynomial x^2 + 4
+                From: Number Field in a1 with defining polynomial x^2 - 2
                 To:   Number Field in a with defining polynomial 2*x^4 + 6*x^2 + 1/2
-                Defn: a2 |--> 2*a^3 + 7*a,
+                Defn: a1 |--> a^2 + 3/2,
               None),
-             (Number Field in a0 with defining polynomial x,
+             (Number Field in a2 with defining polynomial x^2 + 4,
               Ring morphism:
-                From: Number Field in a0 with defining polynomial x
+                From: Number Field in a2 with defining polynomial x^2 + 4
                 To:   Number Field in a with defining polynomial 2*x^4 + 6*x^2 + 1/2
-                Defn: 0 |--> 0,
+                Defn: a2 |--> 2*a^3 + 7*a,
               None),
-             (Number Field in a1 with defining polynomial x^2 - 2,
+             (Number Field in a3 with defining polynomial x^2 + 2,
               Ring morphism:
-                From: Number Field in a1 with defining polynomial x^2 - 2
+                From: Number Field in a3 with defining polynomial x^2 + 2
                 To:   Number Field in a with defining polynomial 2*x^4 + 6*x^2 + 1/2
-                Defn: a1 |--> a^2 + 3/2,
+                Defn: a3 |--> 2*a^3 + 5*a,
               None),
              (Number Field in a4 with defining polynomial x^4 + 1,
               Ring morphism:
@@ -8814,6 +8814,8 @@ def subfields(self, degree=0, name=None):
                 From: Number Field in a with defining polynomial 2*x^4 + 6*x^2 + 1/2
                 To:   Number Field in a4 with defining polynomial x^4 + 1
                 Defn: a |--> -1/2*a4^3 + a4^2 - 1/2*a4)]
+            sage: sorted([F.discriminant() for F, _, _ in l])
+            [-8, -4, 1, 8, 256]
         """
         return self._subfields_helper(degree=degree, name=name,
                                       both_maps=True, optimize=False)