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Testing NixOS Command Not Found Handler Implementation in thefuck

A comprehensive test suite for the NixOS command not found functionality in the thefuck project, validating command matching and installation behavior. The tests ensure proper handling of missing commands and their automated installation suggestions.

Test Coverage Overview

The test suite provides thorough coverage of NixOS command not found handling, focusing on command matching and installation workflows.

Key areas tested include:

Command matching for valid NixOS package suggestions
Negative test cases for invalid or empty commands
Command chaining after package installation

Implementation Analysis

The implementation uses pytest’s parametrize decorator to efficiently test multiple scenarios with minimal code duplication. The testing approach leverages mocking to isolate the command matching logic and verify the correct generation of installation commands.

Technical patterns include:

Parameterized test cases for different command scenarios
Mock patching of system dependencies
Command object handling and transformation

Technical Details

Testing infrastructure includes:

pytest framework for test organization
pytest-mock for dependency mocking
Custom Command type for input handling
Parameterized test cases for coverage efficiency

Best Practices Demonstrated

The test suite exemplifies several testing best practices in Python unit testing. It demonstrates clean separation of concerns, effective use of fixtures, and comprehensive edge case coverage.

Notable practices include:

Isolated test cases with clear purpose
Effective use of parametrization
Proper mocking of external dependencies
Clear test case organization

nvbn/thefuck

tests/rules/test_nixos_cmd_not_found.py

            
import pytest
from thefuck.rules.nixos_cmd_not_found import match, get_new_command
from thefuck.types import Command


@pytest.mark.parametrize('command', [
    Command('vim', 'nix-env -iA nixos.vim')])
def test_match(mocker, command):
    mocker.patch('thefuck.rules.nixos_cmd_not_found', return_value=None)
    assert match(command)


@pytest.mark.parametrize('command', [
    Command('vim', ''),
    Command('', '')])
def test_not_match(mocker, command):
    mocker.patch('thefuck.rules.nixos_cmd_not_found', return_value=None)
    assert not match(command)


@pytest.mark.parametrize('command, new_command', [
    (Command('vim', 'nix-env -iA nixos.vim'), 'nix-env -iA nixos.vim && vim'),
    (Command('pacman', 'nix-env -iA nixos.pacman'), 'nix-env -iA nixos.pacman && pacman')])
def test_get_new_command(mocker, command, new_command):
    assert get_new_command(command) == new_command