Unit Testing django-graphene GraphQL endpoints with pytest
On a project at work I’ve been learning GraphQL. I’m in charge of both developing the backend ( using the wonderful graphene-django package) and the frontend ( using Typescript / Vue.js / axios ) for this specific feature.
After wrapping my head around GraphQL and getting a basic endpoint working I wanted to write some tests to ensure that filtering and other requirements are working as expected.
For a proper End-to-end test I’d usually setup a client and post a json dictionary or such. With End-to-end GraphQL tests you need to send actual GraphQL queries, which makes sense but it feels a bit like SQL Injection.
Below is how I’ve settled organizing and writing my GraphQL tests.
tests/
├── __init__.py
├── conftest.py
├── test_myapp/
│ └── test_schema.py
Because the graphql client will be reused across the django site, I added a global fixture that will automatically load mty project’s schema.
# tests/conftest.py
@pytest.fixture
def graphql_client():
from myproject.schema import schema
from graphene.test import Client
return Client(schema)
In this example I’m testing that I’m filtering data as expected when passing a search parameter.
For setup, first I write a query as its own fixture so I can re-use it throughout the test and it’s clear exactly what is going to be run. Second, I make sure the query uses variables instead of hard-coded values when querying so I can change the input depending on the test. Third, setup a model_bakery fixture for data that I expect to find.
import pytest
from model_bakery import baker
@pytest.mark.django_db
class TestMyModelData:
@pytest.fixture
def query(self):
return """
query testGetMyModel($searchParam: String!){
myModelData(searchParam: $searchParam) {
totalCount
}
}"""
@pytest.fixture
def my_model(self):
baker.make(
"myapp.MyModel",
total_count="20", # Decimal field
)
def test_none_response(self, graphql_client, query, my_model):
executed = graphql_client.execute(query, variables={"searchParam": "skittles"})
assert executed == {"data": {"myModelData": None}}
def test_filters_usage(self, graphql_client, query, my_model):
params = {"searchParam": "skittles"}
executed = graphql_client.execute(query, variables=params)
assert executed == {
"data": {
"myModelData": {
"totalCount": 20
}
}
}
Executing each test I simply pass my query and required variables for the test/query. In this I’m testing the same query twice: once with and one without a searchParameter. My expectation is that I get no results without a search term and data when to my graphql_client fixture.
As the return value from our client is a dictionary, I can simply assert my expecte results with the actual results. If something changes I’ll know immediately.
Using the techniques above I can easily add new tests for my GraphQL endpoint as the available changes or bugs are found.
