import math from django.db.models.functions import Pi from django.test import TestCase from ..models import FloatModel class PiTests(TestCase): def test(self): FloatModel.objects.create(f1=2.5, f2=15.9) obj = FloatModel.objects.annotate(pi=Pi()).first() self.assertIsInstance(obj.pi, float) self.assertAlmostEqual(obj.pi, math.pi, places=5)