createOvermindMock

The createOvermindMock factory creates an instance of Overmind which can be used to test actions. You can mock out effects and evaluate mutations performed during action execution.

overmind/actions.test.ts

import { createOvermindMock } from 'overmind'
import { config } from './'

describe('Actions', () => {
  describe('getPost', () => {
    test('should get post with passed id', async () => {
      const overmind = createOvermindMock(config, {
        api: {
          getPost(id) {
            return Promise.resolve({
              id
            })
          }
        }
      })

      await overmind.actions.getPost('1')

      expect(overmind.mutations).toMatchSnapshot()
    })
    test('should handle errors', async () => {
      const overmind = createOvermindMock(config, {
        api: {
          getPost() {
            throw new Error('test')
          }
        }
      })

      await overmind.actions.getPost('1')

      expect(overmind.mutations).toMatchSnapshot()
    })
  })
})

It is important that you separate your config from the instantiation of Overmind, meaning that createOvermind should not be used in the same file as the config you see imported here, it should rather be used where you render your application. This allows the config to be used for multiple purposes.

Setting initial state

Pass a function as the second or third argument to set initial state.

overmind/actions.test.js

import { createOvermindMock } from 'overmind'
import { config } from './'

describe('State', () => {
  test('should derive authors of posts', async () => {
    const overmind = createOvermindMock(config, (state) => {
      state.posts = { 1: { id: 1, author: 'Janet' } }
    })

    expect(overmind.state.authors).toEqual(['Janet'])
  })
})