"""

Regression tests for proper working of ForeignKey(null=True).

"""

from django.db import models

class SystemDetails(models.Model):

    details = models.TextField()

class SystemInfo(models.Model):

    system_details = models.ForeignKey(SystemDetails)

    system_name = models.CharField(max_length=32)

class Forum(models.Model):

    system_info = models.ForeignKey(SystemInfo)

    forum_name = models.CharField(max_length=32)

class Post(models.Model):

    forum = models.ForeignKey(Forum, null=True)

    title = models.CharField(max_length=32)

    def __unicode__(self):

        return self.title

class Comment(models.Model):

    post = models.ForeignKey(Post, null=True)

    comment_text = models.CharField(max_length=250)

    class Meta:

        ordering = ('comment_text',)

    def __unicode__(self):

        return self.comment_text