Consumer

Requests XML consumer example.

This module defines a simple consumer using the synchronous requests library which will be tested with Pact in the consumer test. As Pact is a consumer-driven framework, the consumer defines the interactions which the provider must then satisfy.

The consumer sends requests expecting XML responses and parses them using the standard library xml.etree.ElementTree module.

This also showcases how Pact tests differ from merely testing adherence to an OpenAPI specification. The Pact tests are more concerned with the practical use of the API, rather than the formally defined specification. So you will see below that the User class includes only the fields this consumer actually needs, id and name, even though the provider could return additional fields in its XML payload.

Note that the code in this module is agnostic of Pact (i.e., this would be your production code). The pact-python dependency only appears in the tests. This is because the consumer is not concerned with Pact, only the tests are.

Attributes

logger = logging.getLogger(__name__) module-attribute

Classes

User(id: int, name: str) dataclass

Represents a user as seen by the consumer.

This class is intentionally minimal, including only the fields the consumer actually uses. It may differ from the provider's user model, which could expose additional fields. This demonstrates the consumer-driven nature of contract testing: the consumer defines what it needs, not what the provider exposes.

Attributes

id: int instance-attribute

name: str instance-attribute

UserClient(hostname: str)

HTTP client for interacting with a user provider service via XML.

PARAMETER	DESCRIPTION
hostname	The base URL of the provider (must include scheme, e.g., http://). TYPE: str

RAISES	DESCRIPTION
ValueError	If the hostname does not start with 'http://' or https://.

Source code in examples/http/xml_example/consumer.py

def __init__(self, hostname: str) -> None:
    """
    Initialise the user client.

    Args:
        hostname:
            The base URL of the provider (must include scheme, e.g.,
            `http://`).

    Raises:
        ValueError:
            If the hostname does not start with 'http://' or `https://`.
    """
    if not hostname.startswith(("http://", "https://")):
        msg = "Invalid base URI"
        raise ValueError(msg)
    self._hostname = hostname
    self._session = requests.Session()

Functions

get_user(user_id: int) -> User

Fetch a user by ID from the provider, expecting an XML response.

PARAMETER	DESCRIPTION
user_id	The ID of the user to fetch. TYPE: int

RETURNS	DESCRIPTION
User	A User instance parsed from the XML response.

RAISES	DESCRIPTION
HTTPError	If the server returns a non-2xx response.

Source code in examples/http/xml_example/consumer.py

def get_user(self, user_id: int) -> User:
    """
    Fetch a user by ID from the provider, expecting an XML response.

    Args:
        user_id:
            The ID of the user to fetch.

    Returns:
        A `User` instance parsed from the XML response.

    Raises:
        requests.HTTPError:
            If the server returns a non-2xx response.
    """
    logger.debug("Fetching user %s", user_id)
    response = self._session.get(
        f"{self._hostname}/users/{user_id}",
        headers={"Accept": "application/xml"},
    )
    response.raise_for_status()
    # S314: xml.etree.ElementTree is safe here because the XML comes from
    # a trusted provider over a controlled HTTP connection, not from
    # arbitrary user input.
    root = ET.fromstring(response.text)  # noqa: S314
    id_text = root.findtext("id")
    name_text = root.findtext("name")
    if id_text is None or name_text is None:
        msg = "Provider response missing required XML element 'id' or 'name'"
        raise ValueError(msg)
    return User(
        id=int(id_text),
        name=name_text,
    )