Add validators and more tests

I don't think these validators will do anything unless we use them or
are submitting a form, but they're there nonetheless

bookwyrm/models/readthrough.py

@@ -1,6 +1,7 @@
 ''' progress in a book '''
 from django.db import models
 from django.utils import timezone
+from django.core import validators
 
 from .base_model import BookWyrmModel
 
@@ -13,6 +14,7 @@ class ReadThrough(BookWyrmModel):
     user = models.ForeignKey('User', on_delete=models.PROTECT)
     book = models.ForeignKey('Edition', on_delete=models.PROTECT)
     progress = models.IntegerField(
+        validators=[validators.MinValueValidator(0)],
         null=True,
         blank=True)
     progress_mode = models.CharField(
@@ -43,7 +45,7 @@ class ProgressUpdate(BookWyrmModel):
     ''' Store progress through a book in the database. '''
     user = models.ForeignKey('User', on_delete=models.PROTECT)
     readthrough = models.ForeignKey('ReadThrough', on_delete=models.CASCADE)
-    progress = models.IntegerField()
+    progress = models.IntegerField(validators=[validators.MinValueValidator(0)])
     mode = models.CharField(
         max_length=3,
         choices=ProgressMode.choices,

bookwyrm/tests/models/test_readthrough_model.py

@@ -0,0 +1,51 @@
+''' testing models '''
+from django.test import TestCase
+from django.core.exceptions import ValidationError
+
+from bookwyrm import models, settings
+
+
+class ReadThrough(TestCase):
+    ''' some activitypub oddness ahead '''
+    def setUp(self):
+        ''' look, a shelf '''
+        self.user = models.User.objects.create_user(
+            'mouse', 'mouse@mouse.mouse', 'mouseword',
+            local=True, localname='mouse')
+
+        self.work = models.Work.objects.create(
+            title='Example Work'
+        )
+
+        self.edition = models.Edition.objects.create(
+            title='Example Edition',
+            parent_work=self.work
+        )
+        self.work.default_edition = self.edition
+        self.work.save()
+
+        self.readthrough = models.ReadThrough.objects.create(
+            user=self.user,
+            book=self.edition)
+
+    def test_progress_update(self):
+        ''' Test progress updates '''
+        self.readthrough.create_update() # No-op, no progress yet
+        self.readthrough.progress = 10
+        self.readthrough.create_update()
+        self.readthrough.progress = 20
+        self.readthrough.progress_mode = models.ProgressMode.PERCENT
+        self.readthrough.create_update()
+
+        updates = self.readthrough.progressupdate_set \
+                    .order_by('created_date').all()
+        self.assertEqual(len(updates), 2)
+        self.assertEqual(updates[0].progress, 10)
+        self.assertEqual(updates[0].mode, models.ProgressMode.PAGE)
+        self.assertEqual(updates[1].progress, 20)
+        self.assertEqual(updates[1].mode, models.ProgressMode.PERCENT)
+
+        self.readthrough.progress = -10
+        self.assertRaises(ValidationError, self.readthrough.clean_fields)
+        update = self.readthrough.create_update()
+        self.assertRaises(ValidationError, update.clean_fields)