joshink / dsemu

A wrapper around the Datastore emulator for use in tests.

dsemu

Description

dsemu is a simple library to help with testing GCP Datastore code written in Python. The provided Emulator class wraps the Datastore emulator and provides basic functionality such as starting/stopping and reseting the emulator instance from inside the test runner.

Requirements

You must have the gcloud tool installed and available in PATH.

Using existing instance of the emulator

If you're running tests that require datastore access frequently it might be better to keep an instance of the emulator running at all time instead of letting the wrapper start and stop it for the duration of the test run. If an instance of the emulator is running and the required environment variables are correctly set the Emulator wrapper will use the running instance instead of starting a new one and will not tear it down at the end of the test run.

Example usage with pytest

# conftest.py
import pytest
from dsemu import Emulator
from google.cloud import datastore


@pytest.fixture(scope="session")
def emulator():
    with Emulator() as emulator:
        yield emulator


@pytest.fixture(scope="session")
def session_client():
    client = datastore.Client(project="test")
    yield client


@pytest.fixture()
def client(emulator: Emulator, session_client: datastore.Client):
    emulator.reset()
    yield session_client

# datastore_test.py
from google.cloud import datastore


def test_datastore_put_and_get(client: datastore.Client):
    kind = "Task"
    name = "sampletask1"
    task_key = client.key(kind, name)
    task = datastore.Entity(key=task_key)
    task["description"] = "Buy milk"
    client.put(task)

    res = client.get(task_key)
    assert res == task