28147: Doctests

src/sage/rings/polynomial/polynomial_element.pyx

@@ -3642,6 +3642,29 @@ cdef class Polynomial(CommutativeAlgebraElement):
             sage: S = R.fraction_field(); x = S.gen()
             sage: R(1).derivative(R(x))
             0
+
+        Check that :trac:`28147` is fixed::
+
+            sage: R.<x> = GF(65537)[]
+            sage: p = x^4 - 17*x^3 + 2*x^2 - x + 7
+            sage: p.derivative()
+            4*x^3 + 65486*x^2 + 4*x + 65536
+            sage: R.<x> = GF(19^2)[]
+            sage: p = x^4 - 17*x^3 + 2*x^2 - x + 7
+            sage: p.derivative()
+            4*x^3 + 6*x^2 + 4*x + 18
+            sage: R.<x> = GF(2)[]
+            sage: p = x^4 + x^2 + x 
+            sage: p.derivative()
+            1
+
+        Check that :trac:`26844` is fixed by :trac:`28147`::
+
+            sage: A = PolynomialRing(GF(3), name='t')
+            sage: K = A.fraction_field()
+            sage: t = K.gen()
+            sage: t.derivative(t)
+            1
         """
         if var is not None and var != self._parent.gen():
             # call _derivative() recursively on coefficients