Snapshot testing (beta) 


1. Run the sequence

Open up your app and run the sequence you want to test.

2. Create test in debugger

In the debugger there is a button in the sequence list called “Create sequence test”. Select the sequence you just triggered and click this button. The test is copied to the clipboard.

3. Run test

It is recommended to use JEST. Just paste what you have in your clipboard and it will look something like this.

test('should filter on all', () => {
  return Snapshot(main) // main is the main module
    .run('filterClicked', { filter: 'all' })
    .then((snapshot) => {

Run the test to create the first snapshot. Any changes to your app that affects this sequence will be yelled at you by Jest.


Creates the test and returns a promise. Pass it the main module of your application.



Runs a sequence with an optional payload. It returns a promise, passing the snapshot.

  .run('some.sequence', { foo: 'bar' })
  .then((snapshot) => {})


Runs a mutation in the state store before the sequence runs.

Snapshot(main).mutate('set', 'some.state.path', 'someValue')


Mocks out a provider that will be called in the sequence. Can give an optional return value. If provider is called multiple times, you will need multiple calls to mock.

Snapshot(main).mock('someProvider.someMethod', 'someReturnedValue')

The mock can also be a function with (context, ...args) signature where args are the arguments passed in the call to the provider method.

Snapshot(main).mock('someProvider.someMethod', (context, ..args) => {
  // mock operation here


Mocks out a provider with a returned promise that resolves with an optional value.



Mocks out a provider with a returned promise that rejects with an optional value.




The Container you use to expose Cerebral to your components can also be used when testing. This is beneficial if you want to test a section of your UI interacts correctly with the Cerebral app.

import React from 'react'
import { mount } from 'enzyme'
import assert from 'assert'
import { Container } from '@cerebral/react'
import App, { Module } from 'cerebral'

import Button from './Button'

describe('<Button />', () => {
  it('should pass foo state on click', () => {
    const testModule = Module({
      state: {
        foo: 'bar'
      sequences: {
        clicked: ({ props }) => assert.equal(props.foo, 'bar')
    const app = App(testModule)
    const wrapper = mount(
      <Container app={app}>
        <Button />


The runComputed test helper accepts the computed and fixture arguments and returns the computed output.

import { props, state } from 'cerebral'
import { runComputed } from 'cerebral/test'

import multiply from './multiply'

it('should multiply by the specified number', () => {
  const result = runComputed(multiply, {
    state: { number: 5 },
    props: { multiplyBy: 2 }

  assert.equal(result, 10)


The runAction test helper accepts the action and fixture arguments and returns a promise.

import { state } from 'cerebral'
import { runAction } from 'cerebral/test'

import increment from './increment'

it('should increment numbers in state', () => {
  return runAction(increment, { state: { number: 1 } }).then(({ state }) =>
    assert.equal(state.number, 2)

The result object passed when the promise resolves contains state, props and output properties.

  props: {
    // props data received by action
  output: {
    // action output data


The CerebralTest factory returns runSequence, setState and getState functions.

import { CerebralTest } from 'cerebral/test'
import math from './math'

it('should accumulate a count', () => {
  const test = CerebralTest(math) // Expects a Module

  test.setState('count', 0)

  return test.runSequence('plusOne').then(({ state }) => {
    assert.equal(state.count, 1)

    return test.runSequence('plus', { value: 2 }).then(() => {
      assert.equal(test.getState('count'), 3)

Note that state initialized in a module takes precedence over the state property of a fixture. Example:

const fixture = {
  // Override default state in modules
  state: {
    app: {
      showNavigation: true
  modules: {


The optional options argument contain the the following options:

recordActions: true|false|'byName'

import { CerebralTest } from 'cerebral/test'
import math from './math'

it('should accumulate a count', () => {
  const test = CerebralTest(math, {
    recordActions: 'byName'

  test.setState('count', 0)

  return test
    .runSequence('plusOne', {
      incrementBy: 1
    .then(({ increment }) => {
      assert.equal(increment.props.incrementBy, 1)

When recordActions: true is specified each action will record its props/output against its index within the sequence. When recordActions: 'byName' is specified each action will record its output against an named property in the result.

The result object passed when the promise resolves contains state and an object for each named action in the sequence with the same name as the actions with props and output properties.