Jest-fixture-injection NPM

jest-fixture-injection

Jest extension to use fixture-injection.

Note: jest-fixture-injection is still in alpha stage.

fixture-injection is a test helper tool for Jest and Jasmine to inject fixtures into test functions and beforeAll() by leveraging dependency injection.

Test functions use fixtures by declaring the fixture names as arguments.
Fixtures can use other fixtures and fixture-injection manages the dependencies.
Fixtures can have asynchronous setup and teardown in it.
Global fixtures are instantiated in the global scope and shared by multiple test suites (independent workers in Jest) and used as a singleton, whereas local fixtures are instantiated in each local scope.

Usage

Define fixtures in __fixtures__.ts:

import { Provide } from 'jest-fixture-injection'

// Example 1) Simple value
export const foo = 'FOO'

// Example 2) Fixture function to provide a value which requires another fixture `foo`
export const bar = (foo: string) => `BAR(${foo})`

// Example 3) Asynchronous fixture function to provide a value
export const baz = async (provide: Provide, bar: string) => { // requires another fixture `bar`
  // Write setup code here
  await provide(`BAZ(${bar}`) // provide the value
  // `await` above waits until the context (test case or suite) finishes
  // Write teardown code here
}

Use fixtures in test functions or beforeAll():

describe('My test suite', () => {
  let fixtures: { foo?: string } = {}

  beforeAll((foo: string) => { // Inject fixtures to *a suite* by beforeAll()
    fixtures.foo = foo
  })

  test('with fixtures', (bar: string, baz: string) => { // Inject fixtures to *a test case*
    // bar and baz are initialized just before this block
    const { foo } = fixtures // Get fixtures from the suite

    expect(foo).toEqual('FOO')
    expect(bar).toEqual('BAR(FOO)')
    expect(baz).toEqual('BAZ(BAR(FOO))')

    // bar and baz are released just after this block
  })

  // foo is released by hidden afterAll() of this block automatically
})

Set environment variable FI_LOGGING=true to print the log.

FI_LOGGING=true jest

Prerequisite

Node.js >= 10
Jest >= 24

Install/Setup

Basic Setup

Install jest-fixture-injection into your NPM project:

$ npm install --dev jest-fixture-injection

Or, if you use Yarn:

$ yarn add --dev jest-fixture-injection

Define test command in package.json:

{
  "scripts": {
    "test": "jest"
  }
}

Create jest.config.js. You can choose jsdom or node as the test environment:

module.exports = {
  preset: 'jest-fixture-injection',
  testEnvironment: 'jest-fixture-injection/dist/jsdom'
}

Or,

module.exports = {
  preset: 'jest-fixture-injection',
  testEnvironment: 'jest-fixture-injection/dist/node'
}

Create fixture-injection.config.js:

module.exports = {
  fixtures: '<rootDir>/tests/__fixtures__.ts',
  globalFixtures: '<rootDir>/tests/__global_fixtures__.ts',
  ipc: {
    appspace: 'my-app'
  }
}

Create your local fixtures in tests/__fixures__.ts
Create your global fixtures in tests/__global_fixtures__.ts
Set ipc.appspace
- It must be unique when you use jest-fixture-injection in multiple processes at a time
- It will be used as the socket file name prefix (e.g., socket file: /tmp/my-app-fixutre-injection-server)
You can set other IPC options; See node-ipc/IPC Config

Create React App

Because Create React App does not allow Jest to read jest.config.js, you have to specify individual command-line options: --env, --globalSetup and --globalTeardown.

package.json:

{
  "scripts": {
    "test": "react-scripts test --env=jest-fixture-injection/dist/jsdom --globalSetup=jest-fixture-injection/dist/setup --globalTeardown=jest-fixture-injection/dist/teardown"
  }
}

Create React App enables @types/jest by default and it conflicts with type definitions of jest-fixture-injection. Set tsconfig.json -> compilerOptions -> types manually to exclude @types/jest from it.

tsconfig.json:

{
  "compilerOptions": {
    "types": ["node", "react", "react-dom", "jest-fixture-injection"]
  }
}

Limitations

done() is not available to define asynchronous tests; Use async/await instead
Don't use transpiler plugins/settings which modify function arguments such as transform-async-to-generator plugin for Babel because fixture-injection parses the argument names at runtime to determine which fixtures to inject.