Migrate test_json to pytest engine

Author: insspb

tests/test_json.py

@@ -0,0 +1,43 @@
+import flask
+import pytest
+
+from flask_mongoengine import MongoEngine
+
+
+@pytest.fixture()
+def extended_db(app):
+    app.json_encoder = DummyEncoder
+    app.config["MONGODB_HOST"] = "mongodb://localhost:27017/flask_mongoengine_test_db"
+    test_db = MongoEngine(app)
+    db_name = test_db.connection.get_database("flask_mongoengine_test_db").name
+
+    if not db_name.endswith("_test_db"):
+        raise RuntimeError(
+            f"DATABASE_URL must point to testing db, not to master db ({db_name})"
+        )
+
+    # Clear database before tests, for cases when some test failed before.
+    test_db.connection.drop_database(db_name)
+
+    yield test_db
+
+    # Clear database after tests, for graceful exit.
+    test_db.connection.drop_database(db_name)
+
+
+class DummyEncoder(flask.json.JSONEncoder):
+    """
+    An example encoder which a user may create and override
+    the apps json_encoder with.
+    This class is a NO-OP, but used to test proper inheritance.
+    """
+
+
+@pytest.mark.usefixtures("extended_db")
+def test_inheritance(app):
+    assert issubclass(app.json_encoder, DummyEncoder)
+    json_encoder_name = app.json_encoder.__name__
+
+    # Since the class is dynamically derrived, must compare class names
+    # rather than class objects.
+    assert json_encoder_name == "MongoEngineJSONEncoder"