django/tests/db_functions/math/test_log.py

import math
from decimal import Decimal

from django.db.models.functions import Log
from django.test import TestCase

from ..models import DecimalModel, FloatModel, IntegerModel


class LogTests(TestCase):
    def test_null(self):
        IntegerModel.objects.create(big=100)
        obj = IntegerModel.objects.annotate(
            null_log_small=Log("small", "normal"),
            null_log_normal=Log("normal", "big"),
            null_log_big=Log("big", "normal"),
        ).first()
        self.assertIsNone(obj.null_log_small)
        self.assertIsNone(obj.null_log_normal)
        self.assertIsNone(obj.null_log_big)

    def test_decimal(self):
        DecimalModel.objects.create(n1=Decimal("12.9"), n2=Decimal("3.6"))
        obj = DecimalModel.objects.annotate(n_log=Log("n1", "n2")).first()
        self.assertIsInstance(obj.n_log, Decimal)
        self.assertAlmostEqual(obj.n_log, Decimal(math.log(obj.n2, obj.n1)))

    def test_float(self):
        FloatModel.objects.create(f1=2.0, f2=4.0)
        obj = FloatModel.objects.annotate(f_log=Log("f1", "f2")).first()
        self.assertIsInstance(obj.f_log, float)
        self.assertAlmostEqual(obj.f_log, math.log(obj.f2, obj.f1))

    def test_integer(self):
        IntegerModel.objects.create(small=4, normal=8, big=2)
        obj = IntegerModel.objects.annotate(
            small_log=Log("small", "big"),
            normal_log=Log("normal", "big"),
            big_log=Log("big", "big"),
        ).first()
        self.assertIsInstance(obj.small_log, float)
        self.assertIsInstance(obj.normal_log, float)
        self.assertIsInstance(obj.big_log, float)
        self.assertAlmostEqual(obj.small_log, math.log(obj.big, obj.small))
        self.assertAlmostEqual(obj.normal_log, math.log(obj.big, obj.normal))
        self.assertAlmostEqual(obj.big_log, math.log(obj.big, obj.big))