models.py

from django.db import models
from django.utils import timezone

class Zone(models.Model):
    ''' Generic Zone superclass. '''
    name = models.CharField(max_length=35)


class Farm(Zone):
    ''' Farm. Users can have many of these. '''


class Subzone(Zone):
    ''' Subzone, zone within a Farm '''
    farm = models.ForeignKey(Farm)


class Device(models.Model):
    ''' Generic device superclass. '''
    name = models.CharField(max_length=35)
    zone = models.ForeignKey(Zone)


class TemperatureAlarm(models.Model):
    ''' Temperature alarm functionality for the A1. '''
    temperature = models.FloatField()
    trigger_type = models.CharField(max_length=35)

    def trigger(self):
        pass


class A1(Device):
    ''' A1 device from FAVEGA. Temperature probe. '''
    alarm = models.ForeignKey(TemperatureAlarm)

    def average_temperature(self, start, end=timezone.now()):
        temps = list()
        for temperature in self.temperature_set.all():
            if temperature.date < end and temperature.date > start:
                temps.append(temperature.temperature)
        return sum(temps) / len(temps) if len(temps) > 0 else 1


class Temperature(models.Model):
    temperature = models.FloatField()
    date = models.DateTimeField(auto_now=True)
    device = models.ForeignKey(A1)

tests.py

from django.test import TestCase
from django.utils import timezone
from datetime import timedelta
from FarmNet.models import A1, TemperatureAlarm, Temperature, Farm


class A1TestCase(TestCase):
    def setUp(self):
        alarm = TemperatureAlarm.objects.create(temperature=30.0)
        alarm.save()
        farm = Farm(name='Granja Ejea')
        farm.save()
        A1.objects.create(name="A1 exterior", alarm=alarm, zone=farm)

    def test_add_temperature(self):
        a1 = A1.objects.get(name="A1 exterior")
        temp = Temperature(device=a1, temperature=30.0,
                           date=timezone.now())
        a1.save()
        temp.save()
        self.assertIn(temp, a1.temperature_set.all())

    def test_average_temperature(self):
        a1 = A1.objects.get(name="A1 exterior")
        temp1 = Temperature(device=a1, temperature=30.0,
                            date=timezone.now() -
                            timedelta(hours=8))
        temp2 = Temperature(device=a1, temperature=20.0)
        a1.save()
        temp1.save()
        temp2.save()
        self.assertEquals(25.0, a1.average_temperature(timezone.now() -
                                                       timedelta(hours=9)))