text: """
  Spanning tests for all the operations that F() expressions can perform.
  """
  
  from django.db import models
  
  #
  # Model for testing arithmetic expressions.
  #
  
  class Number(models.Model):
      integer = models.IntegerField()
      float = models.FloatField(null=True)
  
      def __unicode__(self):
          return u'%i, %.3f' % (self.integer, self.float)
  
  
  __test__ = {'API_TESTS': """
  >>> from django.db.models import F
  
  >>> Number(integer=-1).save()
  >>> Number(integer=42).save()
  >>> Number(integer=1337).save()
  
  We can fill a value in all objects with an other value of the same object.
  
  >>> Number.objects.update(float=F('integer'))
  3
  >>> Number.objects.all()
  [<Number: -1, -1.000>, <Number: 42, 42.000>, <Number: 1337, 1337.000>]
  
  We can increment a value of all objects in a query set.
  
  >>> Number.objects.filter(integer__gt=0).update(integer=F('integer') + 1)
  2
  >>> Number.objects.all()
  [<Number: -1, -1.000>, <Number: 43, 42.000>, <Number: 1338, 1337.000>]
  
  We can filter for objects, where a value is not equals the value of an other field.
  
  >>> Number.objects.exclude(float=F('integer'))
  [<Number: 43, 42.000>, <Number: 1338, 1337.000>]
  
  Complex expressions of different connection types are possible.
  
  >>> n = Number.objects.create(integer=10, float=123.45)
  
  >>> Number.objects.filter(pk=n.pk).update(float=F('integer') + F('float') * 2)
  1
  >>> Number.objects.get(pk=n.pk)
  <Number: 10, 256.900>
  
  # All supported operators work as expected.
  
  >>> n = Number.objects.create(integer=42, float=15.5)
  
  # Left hand operators
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=F('integer') + 15, float=F('float') + 42.7)
  >>> Number.objects.get(pk=n.pk) # LH Addition of floats and integers
  <Number: 57, 58.200>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=F('integer') - 15, float=F('float') - 42.7)
  >>> Number.objects.get(pk=n.pk) # LH Subtraction of floats and integers
  <Number: 27, -27.200>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=F('integer') * 15, float=F('float') * 42.7)
  >>> Number.objects.get(pk=n.pk) # Multiplication of floats and integers
  <Number: 630, 661.850>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=F('integer') / 2, float=F('float') / 42.7)
  >>> Number.objects.get(pk=n.pk) # LH Division of floats and integers
  <Number: 21, 0.363>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=F('integer') % 20)
  >>> Number.objects.get(pk=n.pk) # LH Modulo arithmetic on integers
  <Number: 2, 15.500>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=F('integer') & 56)
  >>> Number.objects.get(pk=n.pk) # LH Bitwise ands on integers
  <Number: 40, 15.500>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=F('integer') | 48)
  >>> Number.objects.get(pk=n.pk) # LH Bitwise or on integers
  <Number: 58, 15.500>
  
  # Right hand operators
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=15 + F('integer'), float=42.7 + F('float'))
  >>> Number.objects.get(pk=n.pk) # RH Addition of floats and integers
  <Number: 57, 58.200>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=15 - F('integer'), float=42.7 - F('float'))
  >>> Number.objects.get(pk=n.pk) # RH Subtraction of floats and integers
  <Number: -27, 27.200>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=15 * F('integer'), float=42.7 * F('float'))
  >>> Number.objects.get(pk=n.pk) # RH Multiplication of floats and integers
  <Number: 630, 661.850>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=640 / F('integer'), float=42.7 / F('float'))
  >>> Number.objects.get(pk=n.pk) # RH Division of floats and integers
  <Number: 15, 2.755>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=69 % F('integer'))
  >>> Number.objects.get(pk=n.pk) # RH Modulo arithmetic on integers
  <Number: 27, 15.500>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=15 & F('integer'))
  >>> Number.objects.get(pk=n.pk) # RH Bitwise ands on integers
  <Number: 10, 15.500>
  
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
  >>> _ = Number.objects.filter(pk=n.pk).update(integer=15 | F('integer'))
  >>> Number.objects.get(pk=n.pk) # RH Bitwise or on integers
  <Number: 47, 15.500>
  
  
  """}
  