Execution order of Jest/Jasmine test code

README.md

Execution order of Jest/Jasmine test code

While tests run in source order, surrounding code does not which can lead to hard to debug issues.

Compare the test file below with the sample output below that and note the order of the log messages.

Key points

• Any code not inside of it, beforeAll, afterAll, beforeEach or afterEach runs immediately on initialisation.
  • This means code at the end of your file runs before even your before hooks.
  • Code inside a describe block runs even if the block or file has no active tests.
• *All hooks wrap *Each hooks, i.e.
  • For a given test all beforeAll hooks will have run before the first beforeEach hook runs, regardless of the order in which they are defined and nested.
  • Similarly afterAll hooks run after all afterEach hooks.

How to run it

If you want to try this yourself:

• Install Jest npm i -g jest
• Save runOrder.test.js in a folder (ensure it is named with .test.js as a suffix)
• Run jest in that folder

runOrder.test.js

/**
 * Demonstrate execution order of code in Jest/Jasmine
 */

console.log('Before describes');

describe('First test', () => {

  console.log('Inside first test describe');

  beforeAll(() => console.log('Before all'));
  afterAll(() => console.log('After all'));
  beforeEach(() => console.log('Before each'));
  afterEach(() => console.log('After each'));

  describe('Inner', () => {
    beforeAll(() => console.log('Before all inner'));
    afterAll(() => console.log('After all inner'));
    beforeEach(() => console.log('Before each inner'));
    afterEach(() => console.log('After each inner'));

    it('runs a test', () => console.log('>>> Running first test'));
    it('runs another test', () => console.log('>>> Running second test'));
  });

  it('runs this test too', () => console.log('>>> Running third test'));
});

console.log('Between describes');

describe('Second test', () => {

  console.log('Inside second test describe');

  it.skip('doesn\'t run this test', () => console.log('Nope'));

});

console.log('After describes');

terminal-log.txt

$ jest
 PASS  ./runOrder.test.js
  First test
    ✓ runs this test too
    Inner
      ✓ runs a test (1ms)
      ✓ runs another test
  Second test
    ○ doesn't run this test

Test Suites: 1 passed, 1 total
Tests:       1 skipped, 3 passed, 4 total
Snapshots:   0 total
Time:        0.619s, estimated 1s
Ran all test suites.
  console.log runOrder.test.js:10
    Before describes

  console.log runOrder.test.js:14
    Inside first test describe

  console.log runOrder.test.js:34
    Between describes

  console.log runOrder.test.js:38
    Inside second test describe

  console.log runOrder.test.js:44
    After describes

  console.log runOrder.test.js:16
    Before all

  console.log runOrder.test.js:22
    Before all inner

  console.log runOrder.test.js:18
    Before each

  console.log runOrder.test.js:24
    Before each inner

  console.log runOrder.test.js:27
    >>> Running first test

  console.log runOrder.test.js:25
    After each inner

  console.log runOrder.test.js:19
    After each

  console.log runOrder.test.js:18
    Before each

  console.log runOrder.test.js:24
    Before each inner

  console.log runOrder.test.js:28
    >>> Running second test

  console.log runOrder.test.js:25
    After each inner

  console.log runOrder.test.js:19
    After each

  console.log runOrder.test.js:23
    After all inner

  console.log runOrder.test.js:18
    Before each

  console.log runOrder.test.js:31
    >>> Running third test

  console.log runOrder.test.js:19
    After each

  console.log runOrder.test.js:17
    After all

async version of above, fwiw: https://gist.github.com/chuckplantain/8359063a1c025b5ccfce52b4f5707368