diff --git a/tests/test_db.py b/tests/test_db.py
index f155064..e26c535 100644
--- a/tests/test_db.py
+++ b/tests/test_db.py
@@ -197,6 +197,16 @@ def test_db_parsing(url, engine, name, host, user, passwd, port):
         assert config['OPTIONS'] == {'reconnect': 'true'}
 
 
+def test_custom_db_engine():
+    """Override ENGINE determined from schema."""
+    env_url = 'postgres://enigma:secret@example.com:5431/dbname'
+
+    engine = 'mypackage.backends.whatever'
+    url = Env.db_url_config(env_url, engine=engine)
+
+    assert url['ENGINE'] == engine
+
+
 def test_postgres_complex_db_name_parsing():
     """Make sure we can use complex postgres host."""
     env_url = (
diff --git a/tests/test_email.py b/tests/test_email.py
index c59ad83..1c9a875 100644
--- a/tests/test_email.py
+++ b/tests/test_email.py
@@ -22,3 +22,13 @@ def test_smtp_parsing():
     assert url['EMAIL_PORT'] == 587
     assert url['EMAIL_USE_TLS'] is True
     assert url['EMAIL_FILE_PATH'] == ''
+
+
+def test_custom_email_backend():
+    """Override EMAIL_BACKEND determined from schema."""
+    url = 'smtps://user@domain.com:password@smtp.example.com:587'
+
+    backend = 'mypackage.backends.whatever'
+    url = Env.email_url_config(url, backend=backend)
+
+    assert url['EMAIL_BACKEND'] == backend
diff --git a/tests/test_search.py b/tests/test_search.py
index 8130921..38f11f7 100644
--- a/tests/test_search.py
+++ b/tests/test_search.py
@@ -86,6 +86,16 @@ def test_elasticsearch_parsing(url, engine, scheme):
     assert url["URL"].startswith(scheme + ":")
 
 
+def test_custom_search_engine():
+    """Override ENGINE determined from schema."""
+    env_url = 'elasticsearch://127.0.0.1:9200/index'
+
+    engine = 'mypackage.backends.whatever'
+    url = Env.db_url_config(env_url, engine=engine)
+
+    assert url['ENGINE'] == engine
+
+
 @pytest.mark.parametrize('storage', ['file', 'ram'])
 def test_whoosh_parsing(whoosh_url, storage):
     post_limit = 128 * 1024 * 1024