Testing Guide¶

Comprehensive testing practices.

Test Structure¶

tests/
├── unit/                    # Unit tests
│   ├── test_genotype.py     # Tree structure tests
│   ├── test_ga_operators.py # GA operator tests
│   └── test_fitness.py      # Fitness calculation tests
├── integration/             # Integration tests
│   └── test_end_to_end.py   # Full workflow tests
└── conftest.py              # Shared fixtures

Running Tests¶

# All tests
pytest tests/ -v

# Specific category
pytest tests/unit/ -v
pytest tests/integration/ -v

# Specific file
pytest tests/unit/test_genotype.py -v

# With coverage
pytest tests/ -v --cov=src/ga_trees --cov-report=html

# Parallel execution
pytest tests/ -n auto

Writing Tests¶

AAA Pattern¶

Arrange-Act-Assert:

def test_tree_crossover():
    # Arrange
    parent1 = create_sample_tree(depth=2)
    parent2 = create_sample_tree(depth=2)

    # Act
    child1, child2 = Crossover.subtree_crossover(parent1, parent2)

    # Assert
    assert child1.get_depth() <= parent1.max_depth
    assert child2.get_depth() <= parent2.max_depth
    assert child1 is not parent1  # New instance

Test Naming¶

# Good - descriptive
def test_mutation_reduces_tree_size_when_pruning():
    pass


def test_fitness_increases_with_accuracy():
    pass


# Bad - vague
def test_mutation():
    pass


def test_tree():
    pass

Fixtures¶

Define in conftest.py:

import pytest
from sklearn.datasets import load_iris


@pytest.fixture
def iris_data():
    """Load Iris dataset."""
    return load_iris(return_X_y=True)


@pytest.fixture
def simple_tree():
    """Create simple 3-node tree."""
    left = create_leaf_node(0, 1)
    right = create_leaf_node(1, 1)
    root = create_internal_node(0, 0.5, left, right, 0)
    return TreeGenotype(root=root, n_features=4, n_classes=2)

Use in tests:

def test_tree_prediction(simple_tree, iris_data):
    X, y = iris_data
    predictor = TreePredictor()
    y_pred = predictor.predict(simple_tree, X)
    assert len(y_pred) == len(y)

Test Coverage¶

Target: 80%+ overall

Check coverage:

pytest tests/ --cov=src/ga_trees --cov-report=term-missing

View HTML report:

pytest tests/ --cov=src/ga_trees --cov-report=html
open htmlcov/index.html

Best Practices¶

Test public API: Don't test private methods
One assertion per concept: Split complex tests
Descriptive names: Test name explains what's tested
Fast tests: Use small datasets, mock when needed
Isolated tests: No dependencies between tests
Deterministic: Set random seeds