Python

Tests should be useful

Python clean test tip:

Tests should protect you against regressions. They shouldn't just increase your code coverage percentage. Make sure they are useful! Don't just write tests for the sake of writing tests. They are code too, so they need to be maintained.

Example:

from dataclasses import dataclass


@dataclass
class User:
    first_name: str
    last_name: str

    def fullname(self):
        return f"{self.first_name} {self.last_name}"


# BAD
def test_full_name():
    user = User(first_name="John", last_name="Doe")
    assert user.fullname() is not None


# GOOD
def test_full_name_consists_of_first_name_and_last_name():
    first_name = "John"
    last_name = "Doe"
    full_name = "John Doe"
    user = User(first_name=first_name, last_name=last_name)

    assert user.fullname() == full_name