5.4Higher-Order Functions

A higher-order function takes a function as an argument or returns a function. They are the building blocks of flexible test utilities.

Custom Assertion Builder

def assert_response(response, status=None, contains=None, excludes=None):
    """Flexible response assertion."""
    if status is not None:
        assert response.status_code == status, \
            f"Expected {status}, got {response.status_code}: {response.text[:200]}"

    if contains is not None:
        body = response.json()
        for key in contains:
            assert key in body, f"Response missing field: {key}"

    if excludes is not None:
        body = response.json()
        for key in excludes:
            assert key not in body, f"Response contains forbidden field: {key}"

# Usage
assert_response(r, status=200, contains=["id", "name"], excludes=["password"])

Test Data Generator

def make_user_factory(defaults: dict):
    """Creates a factory that generates user data with overrides."""
    counter = 0
    def create(**overrides):
        nonlocal counter
        counter += 1
        user = {**defaults, **overrides}
        user["email"] = user.get("email", f"testuser{counter}@test.com")
        return user
    return create

create_user = make_user_factory({"role": "viewer", "active": True})

# Each call creates a unique user with defaults
user1 = create_user()                          # testuser1@test.com, viewer, active
user2 = create_user(role="admin")              # testuser2@test.com, admin, active
user3 = create_user(email="custom@test.com")   # custom@test.com, viewer, active