Test 02 Message Consumer

Consumer test of example message handler using the v3 API.

This test will create a pact between the message handler and the message provider.

Attributes

log = logging.getLogger(__name__) module-attribute

Classes

Functions

handler() -> Handler

Fixture for the Handler.

This fixture mocks the filesystem calls in the handler, so that we can verify that the handler is calling the filesystem correctly.

Source code in examples/tests/v3/test_02_message_consumer.py

@pytest.fixture
def handler() -> Handler:
    """
    Fixture for the Handler.

    This fixture mocks the filesystem calls in the handler, so that we can
    verify that the handler is calling the filesystem correctly.
    """
    handler = Handler()
    handler.fs = MagicMock()
    handler.fs.write.return_value = None
    handler.fs.read.return_value = "Hello world!"
    return handler

pact() -> Generator[Pact, None, None]

Set up Message Pact Consumer.

This fixtures sets up the Message Pact consumer and the pact it has with a provider. The consumer defines the expected messages it will receive from the provider, and the Python test suite verifies that the correct actions are taken.

The verify method takes a function as an argument. This function will be called with one or two arguments - the value of with_body and the contents of with_metadata if provided.

If the function under test does not take those parameters, you can create a wrapper function to convert the pact parameters into the values expected by your function.

For each interaction, the consumer defines the following:

(
    pact = Pact("consumer name", "provider name")
    processed_messages: list[MessagePact.MessagePactResult] = pact             .with_specification("V3")
        .upon_receiving("a request", "Async")             .given("a request to write test.txt")             .with_body(msg)             .with_metadata({"Content-Type": "application/json"})
        .verify(pact_handler)
)

Source code in examples/tests/v3/test_02_message_consumer.py

@pytest.fixture(scope="module")
def pact() -> Generator[Pact, None, None]:
    """
    Set up Message Pact Consumer.

    This fixtures sets up the Message Pact consumer and the pact it has with a
    provider. The consumer defines the expected messages it will receive from
    the provider, and the Python test suite verifies that the correct actions
    are taken.

    The verify method takes a function as an argument. This function
    will be called with one or two arguments - the value of `with_body` and
    the contents of `with_metadata` if provided.

    If the function under test does not take those parameters, you can create
    a wrapper function to convert the pact parameters into the values
    expected by your function.


    For each interaction, the consumer defines the following:

    ```python
    (
        pact = Pact("consumer name", "provider name")
        processed_messages: list[MessagePact.MessagePactResult] = pact \
            .with_specification("V3")
            .upon_receiving("a request", "Async") \
            .given("a request to write test.txt") \
            .with_body(msg) \
            .with_metadata({"Content-Type": "application/json"})
            .verify(pact_handler)
    )

    ```
    """
    pact_dir = Path(Path(__file__).parent.parent.parent / "pacts")
    pact = Pact("v3_message_consumer", "v3_message_provider")
    log.info("Creating Message Pact with V3 specification")
    yield pact.with_specification("V3")
    pact.write_file(pact_dir, overwrite=True)

test_async_message_handler_read(pact: Pact, handler: Handler, verifier: Callable[[str | bytes | None, Dict[str, Any]], None]) -> None

Create a pact between the message handler and the message provider.

Source code in examples/tests/v3/test_02_message_consumer.py

def test_async_message_handler_read(
    pact: Pact,
    handler: Handler,
    verifier: Callable[[str | bytes | None, Dict[str, Any]], None],
) -> None:
    """
    Create a pact between the message handler and the message provider.
    """
    assert isinstance(handler.fs, MagicMock), "Handler filesystem not mocked"

    (
        pact.upon_receiving("a read request", "Async")
        .given("a request to read test.txt")
        .with_body(
            json.dumps({
                "action": "READ",
                "path": "my_file.txt",
            }),
            "application/json",
        )
        .with_matching_rules({
            "body": {
                "$.path": {
                    "combine": "AND",
                    "matchers": [
                        {"match": "type"},
                    ],
                },
            }
        })
    )
    pact.verify(verifier, "Async")

    handler.fs.read.assert_called_once_with("my_file.txt")

test_async_message_handler_write(pact: Pact, handler: Handler, verifier: Callable[[str | bytes | None, Dict[str, Any]], None]) -> None

Create a pact between the message handler and the message provider.

Source code in examples/tests/v3/test_02_message_consumer.py

def test_async_message_handler_write(
    pact: Pact,
    handler: Handler,
    verifier: Callable[[str | bytes | None, Dict[str, Any]], None],
) -> None:
    """
    Create a pact between the message handler and the message provider.
    """
    assert isinstance(handler.fs, MagicMock), "Handler filesystem not mocked"

    (
        pact.upon_receiving("a write request", "Async")
        .given("a request to write test.txt")
        .with_body(
            json.dumps({
                "action": "WRITE",
                "path": "my_file.txt",
                "contents": "Hello, world!",
            }),
            "application/json",
        )
        .with_matching_rules(
            {
                "body": {
                    "$.path": {
                        "combine": "AND",
                        "matchers": [
                            {"match": "type"},
                        ],
                    }
                }
            },
            "Response",
        )
    )
    pact.verify(verifier, "Async")

    handler.fs.write.assert_called_once_with("my_file.txt", "Hello, world!")

verifier(handler: Handler) -> Generator[Callable[[str | bytes | None, Dict[str, Any]], None], Any, None]

Verifier function for the Pact.

This function is passed to the verify method of the Pact object. It is responsible for taking in the messages (along with the context/metadata) and ensuring that the consumer is able to process the message correctly.

In our case, we deserialize the message and pass it to the (pre-mocked) handler for processing. We then verify that the underlying filesystem calls were made as expected.

Source code in examples/tests/v3/test_02_message_consumer.py

@pytest.fixture
def verifier(
    handler: Handler,
) -> Generator[Callable[[str | bytes | None, Dict[str, Any]], None], Any, None]:
    """
    Verifier function for the Pact.

    This function is passed to the `verify` method of the Pact object. It is
    responsible for taking in the messages (along with the context/metadata)
    and ensuring that the consumer is able to process the message correctly.

    In our case, we deserialize the message and pass it to the (pre-mocked)
    handler for processing. We then verify that the underlying filesystem
    calls were made as expected.
    """
    assert isinstance(handler.fs, MagicMock), "Handler filesystem not mocked"

    def _verifier(msg: str | bytes | None, context: Dict[str, Any]) -> None:
        assert msg is not None, "Message is None"
        data = json.loads(msg)
        log.info(
            "Processing message: ",
            extra={"input": msg, "processed_message": data, "context": context},
        )
        handler.process(data)

    yield _verifier

    assert handler.fs.mock_calls, "Handler did not call the filesystem"