Jestspectation

Pattern matching tools to test complex data structures.

The design is inspired by the expect system from JavaScript's Jest testing framework.

import jestspectation as expect

assert {
    "a": 1,
    "b": 2,
    "c": 3.0,
} == {
    "a": 1,
    "b": expect.Any(int),
    "c": expect.FloatApprox(2.5, magnitude=0.5)
}

Installation

pip install jestspectation

Usage with Pytest

The library can be used as a pytest plugin, which can give access to much more detailed error messages when assertions fail.

This should result in output similar to the following

    def test_goodbye():
>       assert 1 == expect.Any(float)
E       assert Type mismatch
E         Expected any object of type float
E         Received 1 (int)

These advanced completions can also be used for most standard Python objects by wrapping the expected values in an Equals. For example:

    def test_lists():
>       assert expect.Equals([1, 2, 3, 4]) == [1, 2, 3, 5, 6]
E       assert [1, 2, 3, 4] == [1, 2, 3, 5, 6]
E         !! [3] 4 == 5
E            Value mismatch
E            Expected 4
E            Received 5
E         ++ [4] 6

To automatically use Jestspectation's diff parsing, you can configure Jestspectation.

import jestspectation

jestspectation.configure().pytest_all_diffs = True