From 3e02d1cd7f541eede2ee0748bba69f05a25f5dfb Mon Sep 17 00:00:00 2001
From: Vincent Delecroix <vincent.delecroix@u-bordeaux.fr>
Date: Wed, 1 Mar 2023 11:41:45 +0100
Subject: [PATCH] add tests for solved issue #15971

---
 src/sage/rings/fraction_field.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/sage/rings/fraction_field.py b/src/sage/rings/fraction_field.py
index 3f1964b13d2..c1af06dd1e9 100644
--- a/src/sage/rings/fraction_field.py
+++ b/src/sage/rings/fraction_field.py
@@ -55,6 +55,18 @@
     sage: F = FractionField(PolynomialRing(RationalField(),2,'x'))
     sage: F == loads(dumps(F))
     True
+
+Test that :trac:`15971` is fixed::
+
+    sage: for B in [QQ['t'], QQ['s, t'], ZZ['t'], ZZ['s, t']]:
+    ....:     F = B.fraction_field()
+    ....:     R = F['x, y']
+    ....:     x = R.gen(0)
+    ....:     print(x / x)
+    1
+    1
+    1
+    1
 """
 # ****************************************************************************
 #