Increase test coverage

dj_database_url.py

@@ -1,17 +1,17 @@
 import os
 import urllib.parse as urlparse
-
-try:
-    from django import VERSION as DJANGO_VERSION
-except ImportError:
-    DJANGO_VERSION = None
+from importlib import import_module
 
 
 def get_postgres_backend():
     # Django deprecated the `django.db.backends.postgresql_psycopg2` in 2.0.
     # https://docs.djangoproject.com/en/stable/releases/2.0/#id1
-    if DJANGO_VERSION and DJANGO_VERSION < (2, 0):
-        return "django.db.backends.postgresql_psycopg2"
+    try:
+        django = import_module("django")
+        if django.VERSION < (2, 0):
+            return "django.db.backends.postgresql_psycopg2"
+    except ModuleNotFoundError:
+        pass
     return "django.db.backends.postgresql"
 
 

test_dj_database_url.py

@@ -1,6 +1,7 @@
 import os
 import re
 import unittest
+from types import SimpleNamespace
 from unittest.mock import patch
 from urllib.parse import uses_netloc
 
@@ -120,14 +121,24 @@ def test_provide_conn_max_age__use_it_in_final_config(self):
         config = dj_database_url.parse(URL, CONN_MAX_AGE=600)
         assert config["CONN_MAX_AGE"] == 600
 
-    @patch("dj_database_url.DJANGO_VERSION", (1, 11, 0, "final", 1))
-    def test_django_version_pre_2__use_postgresql_psycopg2_backend(self):
+    @patch("dj_database_url.import_module")
+    def test_django_version_pre_2__use_postgresql_psycopg2_backend(self, mock):
+        version = (1, 11, 0, "final", 1)
         expected = "django.db.backends.postgresql_psycopg2"
+        mock.return_value = SimpleNamespace(VERSION=version)
         assert dj_database_url.get_postgres_backend() == expected
 
-    @patch("dj_database_url.DJANGO_VERSION", (3, 2, 0, "final", 0))
-    def test_django_version_post_2__use_postgresql_backend(self):
+    @patch("dj_database_url.import_module")
+    def test_django_version_post_2__use_postgresql_backend(self, mock):
+        version = (3, 2, 0, "final", 0)
         expected = "django.db.backends.postgresql"
+        mock.return_value = SimpleNamespace(VERSION=version)
+        assert dj_database_url.get_postgres_backend() == expected
+
+    @patch("dj_database_url.import_module")
+    def test_no_django_installed__use_postgresql_backend(self, mock):
+        expected = "django.db.backends.postgresql"
+        mock.side_effect = ModuleNotFoundError()
         assert dj_database_url.get_postgres_backend() == expected
 
     def test_register_multiple_times__no_duplicates_in_uses_netloc(self):
@@ -137,7 +148,6 @@ def test_register_multiple_times__no_duplicates_in_uses_netloc(self):
         # that list is short and performs linear search on it.
         dj_database_url.register("django.contrib.db.backends.bag_end", "bag-end")
         dj_database_url.register("django.contrib.db.backends.bag_end", "bag-end")
-
         assert len(uses_netloc) == len(set(uses_netloc))
 
     def test_postgres_parsing(self):