use postgres database in test instead of sqlite

tests/conftest.py

@@ -1,53 +1,49 @@
 import os
 
+# use the tests/test.env config fle
 # flake8: noqa: E402
-
 os.environ["CONFIG"] = os.path.abspath(
     os.path.join(os.path.dirname(os.path.dirname(__file__)), "tests/test.env")
 )
 
 
-# use in-memory database
-# need to set before importing any other module as DB_URI is init at import time
-os.environ["DB_URI"] = "sqlite://"
-
 import pytest
 
 from app.extensions import db
 from server import create_app
 from init_app import add_sl_domains
 
+app = create_app()
+app.config["TESTING"] = True
+app.config["WTF_CSRF_ENABLED"] = False
+app.config["SERVER_NAME"] = "sl.test"
+
+with app.app_context():
+    db.create_all()
+    add_sl_domains()
+
 
 @pytest.fixture
 def flask_app():
-    app = create_app()
-
-    # use in-memory database
-    app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite://"
-    app.config["TESTING"] = True
-    app.config["WTF_CSRF_ENABLED"] = False
-    app.config["SERVER_NAME"] = "sl.test"
-
-    with app.app_context():
-        db.create_all()
-        add_sl_domains()
-
     yield app
 
 
 @pytest.fixture
 def flask_client():
-    app = create_app()
-
-    # use in-memory database
-    app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite://"
-    app.config["TESTING"] = True
-    app.config["WTF_CSRF_ENABLED"] = False
-    app.config["SERVER_NAME"] = "sl.test"
-
-    client = app.test_client()
-
     with app.app_context():
-        db.create_all()
-        add_sl_domains()
-        yield client
+        # replace db.session to that we can rollback all commits that can be made during a test
+        # inspired from http://alexmic.net/flask-sqlalchemy-pytest/
+        connection = db.engine.connect()
+        transaction = connection.begin()
+        options = dict(bind=connection, binds={})
+        session = db.create_scoped_session(options=options)
+        db.session = session
+
+        try:
+            client = app.test_client()
+            yield client
+        finally:
+            # roll back all commits made during a test
+            transaction.rollback()
+            connection.close()
+            session.remove()

tests/test.env

@@ -16,7 +16,7 @@ DKIM_PRIVATE_KEY_PATH=local_data/dkim.key
 
 # Database
 RESET_DB=true
-DB_URI=sqlite:///db.sqlite
+DB_URI=postgresql://db/test
 
 # Flask
 FLASK_SECRET=secret