redux-testkit

redux-testkit

##Testkit for redux reducers and redux actions (thunks or otherwise)

Installation

Install this module via npm with npm install redux-testkit --save-dev

Description

Use this module to easily write unit tests for redux actions, including asynchronous actions using redux-thunk middleware.

Usage - Actions

To import the module in your test file, use import {ActionTest} from 'redux-testkit';

ActionTest provides these methods:

reset()

Simply resets the store, usually you would use this in beforeEach or equivalent in your test suite, for example

beforeEach(() => {
    actionTest.reset();
});

setState(newState)

This sets the redux store state that will be provided via getState to thunks dispatched to the mockStore. Use this to set up a test that depends on an existing state.

Important note: This object is NOT affected by dispatches, or internal dispatches called in tests. This shouldn't cause any problems because thinks should not rely on the reducer logic but should only 'fire and forget' events to the store

dispatchSync(action)

This is the key method for running your tests. Say your thunk is:

export function actionToTest(parameters) {
  return async function(dispatch, getState) {
    //Asynchronous logic with lots of awaits here
  }
}

then you send this to the mockStore with actionTest.dispatchSync(actionToTest(paramObjects));.

The testkit will run this test synchronously and then you can run expect asertations on the output with:

getDispatched()

This is where you do the work in the tests. To unit test an action, you want to test what effect the action has given a specific starting environment. We set up this environment before the test with setState() and by passing parameters. There are three ways a dispatched action can cause effects:

1. By dispatching an object with a type field to the store
2. By dispatching another action to the store
3. By calling some external function

In case 3, you test the effect by mocking the external function. Typically you would extract that logic to a separate class and import it into your action's class, and so you mock it by using a tool like proxyquire when importing you actions into the test suite.

redux-testkit allows you to unit test cases 1 and 2.

getDispatched() returns an array of all the dispatches sent by the tested action, in order. In case 1, the entire object is saved and you can expect it to have a type and other fields, for example:

getDispatched(n) returns an object with data about the dispatched at position n.

expect(getDispatched(0).isPlainObject()). toBeTrue();
expect(getDispatched(0).getType()).toEqual(actionTypes.ACTION_TYPE_1);
expect(getDispatched(0).getParams().otherField).toEqual({some object});

In case 2, the name of the dispatched function is saved, and can be tested like this

expect(uut.getDispatched(1).isFunction()).toBeTrue();
expect(uut.getDispatched(1).getName()).toEqual('name_of_function');

If this is another thunk, then you must name the internal anonymous async function, like this:

export function name_of_function() {
  return async function name_of_function(dispatch, getState) {
  }
}

To test a synchronous action that dispacthes other actions or objects, you should inject the mockDispatch() and getState() from the actionTest. For example:

const result = actions.syncAction(actionTest.mockDispatch, actionTest.getState(), params...);
expect(result).toEqual(123456);
expect(uut.getDispatched()).to....

Usage - Reducers

import {ReducerTest} from 'redux-testkit';

A redux reducer is a function that takes an action object, with a type field, and changes the state. In almost every case the state object itslef must be immutable.

You can enforce immutability by using immutability libraries, but those often have a performance impact.

ReducerTest offers a test absed new way of enforcing immutability, and syntactic sugar for testing redcuers.

ReducerTest takes two arguments in the constructor: the first is the reduce function you want to test, and the second is an option initialState to use for each test.

ReducerTest has two methods:

test(name, params, testEqual)

This uses your testEqual to test a number of cases provided in the params.

params must be an arra of objects with this structure:

{action, expected, state, description} where state and description are optional.

ReducerTest will test each case given in the params, with either the default initial state or the provided state, and asseert that the expected result is equal to the actual result.

To test for immutability, use:

throwOnMutation()

This will set the ReducerTest to throw an exception when the state is mutated in any test then run on it. By testing with ReducerTest with this set, you can insure that your state is immutable without the need for any immutability library.

TODO

[ ] Improve syntax with Matchers - Please open issues to suggest the syntax you'd want!