Writing unit tests

Basic unit test

So you want to test your karton systems, that’s great! The karton core actually comes with a few helper methods to make it a bit easier.

The building block of all karton tests is karton.core.test.KartonTestCase(). It’s a nifty class that wraps around your karton system and allows you to run tasks on it without needing to create a producer. What’s more important however, is that it runs without any Redis or MinIO interaction and thus creates no side effects.

from .math_karton import MathKarton
from karton.core import Task
from karton.core.test import KartonTestCase


class MathKartonTestCase(KartonTestCase):
    """Test a karton that accepts an array of integers in "numbers" payload and
    returns their sum in "result".
    """
    karton_class = MathKarton

    def test_addition(self) -> None:
        # prepare a fake test task that matches the production format
        task = Task({
            "type": "math-task",
        }, payload={
            "numbers": [1, 2, 3, 4],
        })

        # dry-run the fake task on the wrapped karton system
        results = self.run_task(task)

        # prepare a expected output task and check if it matches the one produced
        expected_task = Task({
            "origin": "karton.math",
            "type": "math-result"
        }, payload={
            "result": 10,
        })

        self.assertTasksEqual(results, [expected_task])

Testing resources

That was pretty simple, but what about testing karton systems that accept and spawn payloads containing resources?

karton.core.test.KartonTestCase() already takes care of them for you. Just use normal karton.core.Resource() like you would normally do.

from .reverser_karton import ReverserKarton
from karton.core import Task, Resource
from karton.core.test import KartonTestCase


class ReverserKartonTestCase(KartonTestCase):
    """
    Test a karton that expects a KartonResource in "file" key and spawns a new
    task containing that file reversed.
    """

    karton_class = ReverserKarton

    def test_reverse(self) -> None:
        # prepare input data
        input_data = b"foobarbaz"
        # create fake, mini-independent resources
        input_sample = Resource("sample.txt", input_data)
        output_sample = Resource("sample.txt", input_data[::-1])

        # prepare a fake test task that matches the production format
        task = Task({
            "type": "reverse-task",
        }, payload={
            "file": input_sample
        })

        # dry-run the fake task on the wrapped karton system
        results = self.run_task(task)

        # prepare a expected output task and check if it matches the one produced
        expected_task = Task({
            "origin": "karton.reverser",
            "type": "reverse-result"
        }, payload={
            "file": output_sample,
        })

        self.assertTasksEqual(results, [expected_task])