add additional unit tests, add safety for if the patient gets added t…

…o bacteraemia twice in the same episode (shouldn't happen)

elcid/models.py

@@ -694,6 +694,8 @@ def _get_field_default(cls, name):
 @receiver(post_save, sender=omodels.Tagging)
 def record_positive_blood_culture(sender, instance, **kwargs):
     if instance.value == Bacteraemia.tag:
-        PositiveBloodCultureHistory.objects.get_or_create(
+        pbch, _ = PositiveBloodCultureHistory.objects.get_or_create(
             patient_id=instance.episode.patient.id
         )
+        pbch.when = datetime.datetime.now()
+        pbch.save()

elcid/test/test_models.py

@@ -491,6 +491,27 @@ def test_not_created_on_a_different_tag_save(self):
         self.episode.set_tag_names(["something"], self.user)
         self.assertEqual(self.patient.positivebloodculturehistory_set.count(), 0)
 
+    def test_not_updated_on_other_removal(self):
+        weeks_ago = datetime.datetime(2017, 1, 1)
+        self.episode.set_tag_names(["bacteraemia"], self.user)
+        self.patient.positivebloodculturehistory_set.update(
+            when=weeks_ago
+        )
+        self.episode.set_tag_names(["something"], self.user)
+        pbch = self.patient.positivebloodculturehistory_set.get()
+        self.assertEqual(pbch.when.date(), weeks_ago.date())
+
+    def test_updated_on_repeat_saves(self):
+        weeks_ago = datetime.datetime(2017, 1, 1)
+        self.episode.set_tag_names(["bacteraemia"], self.user)
+        self.patient.positivebloodculturehistory_set.update(
+            when=weeks_ago
+        )
+        self.episode.set_tag_names(["something"], self.user)
+        self.episode.set_tag_names(["bacteraemia"], self.user)
+        pbch = self.patient.positivebloodculturehistory_set.get()
+        self.assertEqual(pbch.when.date(), datetime.date.today())
+
     def test_only_one_instance_created(self):
         self.episode.set_tag_names(["bacteraemia"], self.user)
         self.episode.set_tag_names(["bacteraemia"], self.user)