Add json model snapshots + tests (#32)

* add json model snapshots + tests

* remove python 3.11

.github/workflows/pythonpackage.yml

@@ -10,7 +10,8 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.8, 3.9, 3.10.x]
+        # TODO: add 3.11.x when it's ready! Last checked Oct 31, 2022
+        python-version: [3.9, 3.10.x]
         django-version: ['<4', '>=4']
 
     steps:

ckc/models.py

@@ -1,4 +1,5 @@
 from django.db import models
+from django.utils.timezone import now
 
 
 class SoftDeleteQuerySet(models.QuerySet):
@@ -23,3 +24,35 @@ class Meta:
     def delete(self, *args, **kwargs):
         self.deleted = True
         self.save()
+
+
+class JsonSnapshotModel(models.Model):
+    """This mixin is meant to be inherited by a model class. It creates a snapshot field for the class that it is a part of.
+     This field is used to solidify data at a given point in time.
+
+    The create_json_snapshot() method must be overridden in the class inheriting this mixin. Inside this method you will build
+    a custom JSON object of your model state. Include the fields you wish to be solidified.
+
+    Lastly, call take_snapshot() at the point in your code you want data to be saved. The time and date this occurs will
+    also be saved in a separate field called snapshot_date.
+    """
+    snapshot = models.JSONField(null=True, blank=True, default=dict)
+    snapshot_date = models.DateTimeField(null=True, blank=True)
+
+    class Meta:
+        abstract = True
+
+    def _create_json_snapshot(self) -> dict:
+        """Override this method to take a "snapshot" of the relevant data on this model"""
+        raise NotImplementedError
+
+    def take_snapshot(self, force=False):
+        if not force:
+            assert not self.snapshot, "Can not override an existing snapshot instance."
+
+        self.snapshot = self._create_json_snapshot()
+
+        # TODO: Do we want to test these edge cases?
+        # assert self.snapshot is not None, ""
+
+        self.snapshot_date = now()

setup.cfg

@@ -37,7 +37,7 @@ name = django-ckc
 author = Eric Carmichael
 author_email = [email protected]
 description = tools, utilities, etc. we use across projects @ ckc
-version = 0.0.8
+version = 0.0.9
 url = https://github.com/ckcollab/django-ckc
 keywords =
   django

testproject/testapp/models.py

@@ -2,20 +2,29 @@
 from django.contrib.gis.db.models import PointField
 from django.db import models
 
-from ckc.models import SoftDeletableModel
+from ckc.models import SoftDeletableModel, JsonSnapshotModel
 
 
 User = get_user_model()
 
 
+# ----------------------------------------------------------------------------
+# Testing soft deletable model
+# ----------------------------------------------------------------------------
 class AModel(SoftDeletableModel):
     title = models.CharField(max_length=255, default="I'm a test!")
 
 
+# ----------------------------------------------------------------------------
+# PrimaryKeyWriteSerializerReadField related model
+# ----------------------------------------------------------------------------
 class BModel(models.Model):
     a = models.ForeignKey(AModel, on_delete=models.CASCADE)
 
 
+# ----------------------------------------------------------------------------
+# DefaultCreatedByMixin models
+# ----------------------------------------------------------------------------
 class ModelWithACreator(models.Model):
     created_by = models.ForeignKey(User, on_delete=models.CASCADE)
 
@@ -24,5 +33,25 @@ class ModelWithADifferentNamedCreator(models.Model):
     owner = models.ForeignKey(User, on_delete=models.CASCADE)
 
 
+# ----------------------------------------------------------------------------
+# For testing geo points in factories
+# ----------------------------------------------------------------------------
 class Location(models.Model):
     geo_point = PointField()
+
+
+# ----------------------------------------------------------------------------
+# For testing JSON snapshots
+# ----------------------------------------------------------------------------
+class SnapshottedModel(JsonSnapshotModel, models.Model):
+
+    def _create_json_snapshot(self) -> dict:
+        return {
+            "test": "snapshot"
+        }
+
+
+class SnapshottedModelMissingOverride(JsonSnapshotModel, models.Model):
+    # No _create_json_snapshot here! This is for testing purposes, to confirm we raise
+    # an assertion when this method is missing
+    pass

tests/integration/test_json_model_snapshots.py

@@ -0,0 +1,42 @@
+import pytest
+from rest_framework.test import APITestCase
+
+from testapp.models import SnapshottedModel, SnapshottedModelMissingOverride
+
+
+class TestJsonSnapshottedModels(APITestCase):
+    def test_snapshot_model_asserts_method_must_be_implemented_if_it_is_missing(self):
+        instance = SnapshottedModelMissingOverride()
+
+        # make sure proper error raised when we try to snapshot with a missing method
+        with pytest.raises(NotImplementedError):
+            instance.take_snapshot()
+
+    def test_snapshot_model_save_actually_saves_to_databse(self):
+        instance = SnapshottedModel()
+        instance.take_snapshot()
+
+        # Snapshot was written to model...
+        assert instance.snapshot == {"test": "snapshot"}
+
+        instance.save()
+
+        # Snapshot was saved to database, forreal
+        assert SnapshottedModel.objects.get(snapshot__test="snapshot")
+
+    def test_snapshotting_an_already_snapshotted_model_raises_exception_unless_forced(self):
+        instance = SnapshottedModel()
+        instance.take_snapshot()
+
+        # trying to snapshot already snapshotted model -> shit the bed
+        with pytest.raises(Exception):
+            instance.take_snapshot()
+
+        # Clear snapshot to see if we can re-set it..
+        instance.snapshot = None
+
+        # No exception raised here! And data was properly written
+        instance.take_snapshot(force=True)
+
+        # We were able to re-snapshot
+        assert instance.snapshot == {"test": "snapshot"}