Testing a Framework application is easy. Given that event handlers are plain Python functions that take arguments such as state and payload, you can inject your own and test whether the outcome is correct. This section will use pytest examples.


Accessing the initial state

To get started, import your app’s entry point, main. This will initialise state and make event handlers available. The initial state is available in the module, at main.wf.initial_state provided you imported writer as wf.

Creating states

For testing purposes, you can create your own state using the StreamsyncState class in writer.core. Pass a dictionary when constructing it.

from writer.core import StreamsyncState

artificial_state = StreamsyncState({
    "a": 3,
    "b": 6


The code of a Framework application basically consists of two things:

  1. Initial state
  2. Event handlers

It’s straightforward to test both, as shown below.

The app

import writer as wf

def handle_multiplication(state):
    state["n"] = state["a"]*state["b"]

    "counter": 0,
    "a": 0,
    "b": 0

The tests

from writer.core import WriterState
import main

class TestApp:

    initial_state = main.wf.initial_state
    artificial_state = WriterState({
        "a": 3,
        "b": 2

    def test_counter_must_start_from_zero(self):
        assert self.initial_state["counter"] == 0

    def test_handle_multiplication(self):
        assert self.artificial_state["n"] == 6