Run Jest test suites in groups

Question

I am writing extensive tests for a new API via Jest and supertest. Prior to running the tests, I am setting up a test database and populating it with users:

Test com

Answer 1

Jest test suites are executed in multiple threads, and this is one of its main benefits. Test runs can be completed much faster this way, but the test sequence isn't preserved by design.

It's possible to disable this feature with the runInBand option.

It's possible to pick tests and suites based on their names with the testNamePattern option or based on their paths with testPathPattern option.

Since one suite depends on another one, they possibly could be combined into a single suite in the order they are expected to run. They can still reside in different files (make sure they aren't matched by Jest), e.g.:

// foobar.test.js
describe(..., () => {
  require('foo.partial-test.js');
  require('bar.partial-test.js');
});

The problem is this:

Some of my tests rely upon the success of other tests.

This is the real problem here. The approach that relies on previous a test state is considered flawed in any kind of automated tests.

I don't want to have to meticulously set up testing conditions (for example, creating a bunch of user images artificially before running the tests), because: (1) this is just duplication of logic, and (2) it increases the possibility of something breaking.

There is no need to set up testing conditions (fixtures) artificially. Fixtures can be extracted from existing environment, even from the results of your current tests if you're sure about their quality.

• Redundancy and tautology naturally occur in automated tests, there's nothing wrong with them. Tests can be made DRYer with proper management of fixtures and shared code.

• Quite the contrary, errors are always accumulated. A test that created faulty prerequisites may pass, but another test will fail, thus creating a debugging conundrum.

Answer 2

You can use jest-runner-groups to define and run tests in groups. Once it's installed and added to the Jest configuration, you can tag your tests using docblock notation, like here:

/**
 * Foo tests
 *
 * @group group1/subgroup1
 * @group unit/foo
 */

describe( 'Foo class', () => {
    ...
} );

/**
 * Bar tests
 *
 * @group group1/subgroup2
 * @group unit/bar
 */

describe( 'Bar class', () => {
    ...
} );

Update your jest configuration to specify a new runner:

// jest.config.js
module.exports = {
    ...
    runner: "groups"
};

Then to run a specific group, you need to use --group= argument:

// Using the Jest executable
jest --group=mygroup

// Or npm
npm test -- --group=mygroup

You can also use multiple --group arguments to run multiple groups:

// Will execute tests in the unit/bar and unit/foo groups
npm test -- --group=unit/bar --group=unit/foo

// Will execute tests in the unit group (including unit/bar and unit/foo groups)
npm test -- --group=unit

Answer 3

I have done it with the --testNamePattern flag. Here is the procedure.

Let’s say that you have two groups of tests:

• DevTest for testing in development environment
• ProdTest for testing in production environemnt

If you want to test only those features required for the development environment, you have to add DevTest to the test description:

describe('(DevTest): Test in development environment', () => {
  // Your test
})

describe('(ProdTest): Test in production environment', () => {
  // Your test
})

describe('Test everywhere', () => {
  // Your test
})

After that, you can add commands to your package.json file:

  "scripts": {
    "test": "jest",
    "test:prod": "jest --testNamePattern=ProdTest",
    "test:dev": "jest --testNamePattern=DevTest",
    "test:update": "jest --updateSnapshot"
  }

Command npm test will run all of your tests, since you are not using flag --testNamePattern. If you want to run other tests, just use npm run test:dev for example.

Be careful when naming your test groups though. They are searched with regex in test description and you don't want this command to match other words.