fixed 'possible_values' field of characteristic endpoint

loop that adds values to 'possible_values' used wrong value in conditional. Created test to verify behavior is as expected.

.gitignore

@@ -9,4 +9,5 @@ node_modules
 .vscode
 *.env
 Resources/nginx/ssl/*
-!Resources/nginx/ssl/*.sample.*
+!Resources/nginx/ssl/*.sample.*
+.idea*

pokemon_v2/serializers.py

@@ -487,7 +487,7 @@ class CharacteristicDetailSerializer(serializers.ModelSerializer):
 
         mod = obj.gene_mod_5
         values = []
-        while mod <= 30:
+        while mod <= 31:
             values.append(mod)
             mod += 5
 

pokemon_v2/tests.py

@@ -4337,6 +4337,21 @@ class APITests(APIData, APITestCase):
             "{}{}/stat/{}/".format(TEST_HOST, API_V2, characteristic.stat.pk),
         )
 
+    def test_characteristic_values(self):
+        l = []
+        # check for all 5 possible values of gene_modulo
+        for modulo in range(5):
+            characteristic = self.setup_characteristic_data(gene_mod_5=modulo)
+            # note that 'possible_values' is computed solely from gene_modulo
+            # thus it is fine that our test characteristics are indexed 1-5
+            result = self.client.get(
+                "{}/characteristic/{}/".format(API_V2, characteristic.pk))
+            for i in range(len(result.data['possible_values'])):
+                self.assertEqual(
+                    result.data['possible_values'][i], characteristic.gene_mod_5 + i * 5
+                )
+
+
     # Nature Tests
     def test_nature_api(self):