Class FlaskClient

src/flask/testing.py:108–261

Works like a regular Werkzeug test client but has knowledge about Flask's contexts to defer the cleanup of the request context until the end of a ``with`` block. For general information about how to use this class refer to :class:`werkzeug.test.Client`. .. versionchanged:: 0.12

class FlaskClient(Client):
    """Works like a regular Werkzeug test client but has knowledge about
    Flask's contexts to defer the cleanup of the request context until
    the end of a ``with`` block. For general information about how to
    use this class refer to :class:`werkzeug.test.Client`.

    .. versionchanged:: 0.12
       `app.test_client()` includes preset default environment, which can be
       set after instantiation of the `app.test_client()` object in
       `client.environ_base`.

    Basic usage is outlined in the :doc:`/testing` chapter.
    """

    application: Flask

    def __init__(self, *args: t.Any, **kwargs: t.Any) -> None:
        super().__init__(*args, **kwargs)
        self.preserve_context = False
        self._new_contexts: list[t.ContextManager[t.Any]] = []
        self._context_stack = ExitStack()
        self.environ_base = {
            "REMOTE_ADDR": "127.0.0.1",
            "HTTP_USER_AGENT": f"Werkzeug/{_get_werkzeug_version()}",
        }

    @contextmanager
    def session_transaction(
        self, *args: t.Any, **kwargs: t.Any
    ) -> t.Iterator[SessionMixin]:
        """When used in combination with a ``with`` statement this opens a
        session transaction.  This can be used to modify the session that
        the test client uses.  Once the ``with`` block is left the session is
        stored back.

        ::

            with client.session_transaction() as session:
                session['value'] = 42

        Internally this is implemented by going through a temporary test
        request context and since session handling could depend on
        request variables this function accepts the same arguments as
        :meth:`~flask.Flask.test_request_context` which are directly
        passed through.
        """
        if self._cookies is None:
            raise TypeError(
                "Cookies are disabled. Create a client with 'use_cookies=True'."
            )

        app = self.application
        ctx = app.test_request_context(*args, **kwargs)
        self._add_cookies_to_wsgi(ctx.request.environ)

        with ctx:
            sess = app.session_interface.open_session(app, ctx.request)