Data Driven Testing (DDT)

Unlike other frameworks, lemoncheesecake does not provide a dedicated API allowing a given test function to be run against data defined in an external file. However, a test suite can be built programmatically making it easy to implement data driven tests with any kind of input data.

Here is simple example where the input data is defined in a JSON file (it could have been XML, YAML, CSV, INI, plain text, etc… JSON has been chosen because it’s easy to process and demonstrate). Each data entry defines two operands i and j, expected is the result of their addition .

Project structure:

$ find -type f
./suites/add.py
./project.py
./data.json

Input data (the data.json file):

[
    {
        "name": "one_plus_one",
        "description": "Add one to one",
        "i": 1,
        "j": 1,
        "expected": 2
    },
    {
        "name": "two_plus_two",
        "description": "Add two to two",
        "i": 2,
        "j": 2,
        "expected": 4
    }
]

The test suite module (the suites/add.py file):

import os.path as osp
import json

import lemoncheesecake.api as lcc
from lemoncheesecake.matching import *

PROJECT_DIR = osp.join(osp.dirname(__file__), "..")


@lcc.suite("Add")
class add:
    def __init__(self):
        data = json.load(open(osp.join(PROJECT_DIR, "data.json")))
        for entry in data:
            test = lcc.Test(
                entry["name"], entry["description"],
                self.make_test_func(entry["i"], entry["j"], entry["expected"])
            )
            lcc.add_test_into_suite(test, self)

    @staticmethod
    def make_test_func(i, j, expected):
        def func():
            check_that("%d + %d" % (i, j), i + j, equal_to(expected))
        return func

Tests are added to the suite through lcc.add_test_into_suite. The usual extra metadata (tags, properties, links) can also be associated to the lcc.Test instance through their corresponding attributes. Tests are generated at project load time meaning they are visible to all lcc commands like any other test:

$ lcc show
* add
    - add.one_plus_one
    - add.two_plus_two

You can find this example project here.