fixture-injection

Note: fixture-injection is still in alpha stage.

fixture-injection is a test helper tool for Jest and Jasmine to define and use fixtures easily by leveraging dependency injection.

Fixtures are code that sets up test subjects and the testing environment defined as a value or a function. These fixtures can be injected to beforeAll(), it(), test(), etc. as arguments.

Usage

tests/__fixtures__.js:

// Example 1) Simple value
const foo = 'FOO'
 
// Example 2) Fixture function to provide a value which requires another fixture `foo`
const bar = (foo) => `BAR(${foo})`
 
// Example 3) Asynchronous fixture function to provide a value
const baz = async (provide, bar) => { // 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
}
 
module.exports = {
  foo,
  bar,
  baz
}

example.spec.js:

describe('My test suite', () => {
  let fixtures = {}
 
  beforeAll((foo) => { // Inject fixtures to *a suite* by beforeAll()
    fixtures.foo = foo
  })
 
  test('with fixtures', (bar, baz) => { // 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
})

Features

1. The code in the fixture function can do whatever you want
2. Fixture function can be asynchronous and can have setup and teardown code around await provide()
3. Fixtures are also available in other fixtures, and the dependencies are automatically resolved
   • Asynchronous fixtures are initialized concurrently as much as possible
4. Local fixtures are initialized every time in each injected context
5. Global fixtures are singletons and initialized only once
   • [Jest] They are initialized by Jest runner and will be sent to individual test workers via IPC
6. In-line fixtures are also available by fixture() in each test file

Packages

• fixture-injection
  • Core package of fixture-injection
• jest-fixture-injection
  • Jest extension to use fixture-injection
• jasmine-fixture-injection
  • Jasmine extension to use fixture-injection

Install/Setup

See the documentation of each test framework extension.

• jest-fixture-injection
• jasmine-fixture-injection

Related Work

• pytest
  • pytest is a popular testing framework for Python. fixture-injection was inspired by its fixtures. pytest fixture has a scope (session/module/function) to manage its lifecycle and can be a generator to have setup/teardown logic in it.