Folio

A customizable test framework to build your own test frameworks. Foundation for the Playwright test runner.

Docs

Isolation and flexibility
Writing a test
Writing a configuration file
Creating an environment
Command line
Snapshots
Annotations
- Flaky tests
Parallelism and sharding
- Workers
- Shards
Advanced configuration
Reporters
- Built-in reporters
- Reporter API

Isolation and flexibility

Folio focuses on test isolation and flexibility. This makes it fast, reliable and able to adapt to your specific needs.

Isolation. Tests are isolated by default and can be run independently.

Folio runs tests in parallel by default, making your test suite much faster. Thanks to isolation, Folio reuses processes for multiple tests, suites and file, which makes it even faster.
Flaky tests can be retried without significant overhead, because Folio will only retry the failures, and not the whole suite.
Refactoring tests and moving them around is effortless, since isolated tests do not have inter-dependencies.
You can group tests based on their meaning, instead of their common setup.

Flexibility. Folio includes advanced features, adapting to your specific testing needs.

Leverage TypeScript power with minimal effort.
Run tests in multiple configurations.
Annotate tests as skipped/failed based on configuration.
Generate comprehensive report with your custom test annotations.
Define multiple test types, for example slow tests or smoke tests, and run them differently.

Writing a test

Folio follows the traditional BDD style. However, each test in Folio receives an object with Test Arguments. These arguments are isolated from other tests, which gives Folio numerous advantages.

test('insert an entry', async ({ table }) => {
  await table.insert({ username: 'folio', password: 'testing' });
  const entry = await table.query({ username: 'folio' });
  expect(entry.password).toBe('testing');
});

In the test above, table is a database table created for each test, so multiple tests running in parallel won't step on each other's toes.

Folio uses expect library for test assertions.

Writing a configuration file

Folio requires a configuration file that specifies how to run the tests.

// folio.config.ts

import * as folio from 'folio';

// Configure Folio to look for tests in this directory, and give each test 20 seconds.
folio.setConfig({ testDir: __dirname, timeout: 20000 });

// Create a new test type. For the easiest setup, you need just one.
export const test = folio.newTestType();

// Run tests of this type, giving them two retries.
test.runWith({ tag: 'basic', retries: 2 });

Now, use the created test type in your tests.

// math.spec.ts

import { test } from './folio.config';

test('math works?', () => {
  test.expect(1 + 1).toBe(42);
});

You can run tests with Folio command line:

$ npx folio --reporter=dot
Running 1 test using 1 worker
××F
 1 failed

Creating an environment

Usually, you need some test environment to run the tests. That may be a test database, dev server, mock user data, or anything else the test needs. Folio support creating an environment that is going to be used for multiple tests.

Let's see how to add an environment, based on the example from writing a configuration file section.

// folio.config.ts

import * as folio from 'folio';

folio.setConfig({ testDir: __dirname, timeout: 20000 });

// Type declaration specifies that tests receive a table instance.
export const test = folio.newTestType<{ table: DatabaseTable }>();

class DatabaseEnv {
  host: string;
  database: Database;
  table: DatabaseTable;

  constructor(host: string) {
    this.host = host;
  }

  async beforeAll() {
    // Connect to a database once, it is expensive.
    this.database = await connectToTestDatabase(this.host);
  }

  async beforeEach() {
    // Create a new table for each test and return it.
    this.table = await this.database.createTable();
    return { table: this.table };
  }

  async afterEach() {
    // Do not leave extra tables around.
    await this.table.drop();
  }

  async afterAll() {
    await this.database.disconnect();
  }
}

// Run our tests in two environments, against a local database and a staging database.
test.runWith(new DatabaseEnv('localhost:1234'));
test.runWith(new DatabaseEnv('staging-db.my-company.com:1234'));

In this example we see that tests declare the arguments they need, and environment provides the arguments. We can run tests in multiple configurations when needed.

Folio uses worker processes to run test files. You can specify the maximum number of workers using --workers command line option. By using beforeAll and afterAll methods, environment can set up expensive resources to be shared between tests in each worker process. Folio will reuse the worker process for as many test files as it can, provided their environments match.

Annotations

Unfortunately, tests do not always pass. Folio supports test annotations to deal with failures, flakiness and tests that are not yet ready.

test('basic', async ({ table }) => {
  test.skip(version == 'v2', 'This test crashes the database in v2, better not run it.');
  // Test goes here.
});

test('can insert multiple rows', async ({ table }) => {
  test.fail('Broken test, but we should fix it!');
  // Test goes here.
});

Annotations may be conditional, in which case they only apply when the condition is truthy. Annotations may depend on test arguments. There could be multiple annotations on the same test, possibly in different configurations.

Possible annotations include:

skip marks the test as irrelevant. Folio does not run such a test. Use this annotation when the test is not applicable in some configuration.
fail marks the test as failing. Folio will run this test and ensure it does indeed fail. If the test does not fail, Folio will complain.
fixme marks the test as failing. Folio will not run this test, as opposite to the fail annotation. Use fixme when running the test is slow or crashy.

Flaky tests

Folio deals with flaky tests with retries. Pass the maximum number of retries when running the tests, or set them in the configuration file.

npx folio --retries=3

Failing tests will be retried multiple times until they pass, or until the maximum number of retries is reached. Folio will report all tests that failed at least once:

Running 1 test using 1 worker
××±
1 flaky
  1) my.test.js:1:1

Command line

Just point Folio to your configuration file.

$ npx folio --config=my.config.ts

Run Folio with --help to see all command line options.

$ npx folio --help

Snapshots

Folio includes the ability to produce and compare snapshots. For that, use expect().toMatchSnapshot(). Folio auto-detects the content type, and includes built-in matchers for text, png and jpeg images, and arbitrary binary data.

test('my test', async () => {
  const image = await produceSomePNG();
  expect(image).toMatchSnapshot('optional-snapshot-name.png');
});

Snapshots are stored under __snapshots__ directory by default, configurable via command line or configuration object.

Parallelism and sharding

Folio runs tests in parallel by default, using multiple worker processes.

Workers

Each worker process creates a new environment to run tests. Different environments always run in different workers. By default, Folio reuses the worker as much as it can to make testing faster, but it will create a new worker when retrying tests, after any test failure, to initialize a new environment, or just to speed up test execution if the worker limit is not reached.

The maximum number of worker processes is controlled via command line or configuration object.

Each worker process is assigned a unique sequential index that is accessible through workerInfo object.

Shards

Folio can shard a test suite, so that it can be executed on multiple machines. For that, pass --shard=x/y to the command line. For example, to split the suite into three shards, each running one third of the tests:

$ npx folio --shard=1/3
$ npx folio --shard=2/3
$ npx folio --shard=3/3

Advanced configuration

Configuration object

Configuration file uses setConfig function to provide a global configuration to Folio. It may contain the following properties:

forbidOnly: boolean - Whether to disallow test.only exclusive tests. Useful on CI.
globalTimeout: number - Total timeout in milliseconds for the whole test run.
grep: string | RegExp | (string | RegExp)[] - Patterns to filter tests based on their title.
maxFailures: number - Stop testing after reaching the maximum number of failures.
outputDir: string - Directory to place any artifacts produced by tests.
quiet: boolean - Whether to suppress stdout and stderr from the tests.
repeatEach: number - Each test will be repeated multiple times.
retries: number - Maximum number of retries.
shard: { total: number, current: number } | null - Shard information.
snapshotDir: string - Snapshots directory.
testDir: string - Directory where Folio should search for tests.
testIgnore: string | RegExp | (string | RegExp)[] - Patterns to ignore test files.
testMatch: string | RegExp | (string | RegExp)[] - Patterns to match test files.
timeout: number - Test timeout in milliseconds.
updateSnapshots: boolean - Whether to update snapshots instead of comparing them.
workers: number - The maximum number of worker processes.

// folio.config.ts

import * as folio from 'folio';

folio.setConfig({
  // Typically, you'd place folio.config.ts in the tests directory.
  testDir: __dirname,
  // 20 seconds per test.
  timeout: 20000,
  // Forbid test.only on CI.
  forbidOnly: !!process.env.CI,
  // Two retries for each test.
  retries: 2,
});

workerInfo

Depending on the configuration and failures, Folio might use different number of worker processes to run all the tests. For example, Folio will always start a new worker process after a failing test.

Environment and hooks receive workerInfo in the beforeAll and afterAll calls. The following information is accessible from the workerInfo:

config - Configuration object.
globalSetupResult - The value returned by the global setup function.
workerIndex: number - A unique sequential index assigned to the worker process.

Consider an example where we run a new http server per worker process, and use workerIndex to produce a unique port number:

import * as http from 'http';

class ServerEnv {
  server: http.Server;

  async beforeAll(workerInfo) {
    this.server = http.createServer();
    this.server.listen(9000 + workerInfo.workerIndex);
    await new Promise(ready => this.server.once('listening', ready));
  }

  async beforeEach() {
    // Provide the server as a test argument.
    return { server: this.server };
  }

  async afterAll() {
    await new Promise(done => this.server.close(done));
  }
}

testInfo

Environment and hooks receive testInfo in the beforeEach and afterEach calls. It is also available to the test function as a second parameter.

In addition to everything from the workerInfo, the following information is accessible before and during the test:

title: string - Test title.
file: string - Full path to the test file.
line: number - Line number of the test declaration.
column: number - Column number of the test declaration.
fn: Function - Test body function.
repeatEachIndex: number - The sequential repeat index.
retry: number - The sequential number of the test retry (zero means first run).
expectedStatus: 'passed' | 'failed' | 'timedOut' - Whether this test is expected to pass, fail or timeout.
timeout: number - Test timeout.
testOptions - Test options.
annotations - Annotations that were added to the test.
data: object - Any additional data that you'd like to attach to the test, it will appear in the report.
snapshotPathSegment: string - Relative path, used to locate snapshots for the test.
snapshotPath(...pathSegments: string[]) - Function that returns the full path to a particular snapshot for the test.
outputPath(...pathSegments: string[]) - Function that returns the full path to a particular output artifact for the test.

The following information is accessible after the test body has finished, in afterEach:

duration: number - test running time in milliseconds.
status: 'passed' | 'failed' | 'timedOut' - the actual test result.
error - any error thrown by the test body.
stdout: (string | Buffer)[] - array of stdout chunks collected during the test run.
stderr: (string | Buffer)[] - array of stderr chunks collected during the test run.

Here is an example test that saves some information:

test('my test needs a file', async ({ table }, testInfo) => {
  // Do something with the table...
  // ... and then save contents.
  const filePath = testInfo.outputPath('table.dat');
  await table.saveTo(filePath);
});

Here is an example environment that automatically saves debug logs when the test fails:

import * as debug from 'debug';
import * as fs from 'fs';

class LogEnv {
  async beforeEach() {
    this.logs = [];
    debug.log = (...args) => this.logs.push(args.map(String).join(''));
    debug.enable('mycomponent');
  }

  async afterEach(testInfo) {
    if (testInfo.status !== testInfo.expectedStatus)
      fs.writeFileSync(testInfo.outputPath('logs.txt'), this.logs.join('\n'), 'utf8');
  }
}

Multiple test types and configurations

Often times there is a need for different kinds of tests, for example generic tests that use a database table, or some specialized tests that require more elaborate setup. It is also common to run tests in multiple configurations. Folio allows you to configure everything by writing code for maximum flexibility.

// folio.config.ts

import * as folio from 'folio';
import * as fs from 'fs';

// 20 seconds timeout, 3 retries by default.
folio.setConfig({ testDir: __dirname, timeout: 20000, retries: 3 });

// Define as many test types as you'd like:
// - Generic test that only needs a string value.
export const test = folio.newTestType<{ value: string }>();
// - Slow test for extra-large data sets.
export const slowTest = folio.newTestType<{ value: string }>();
// - Smoke tests should not be flaky.
export const smokeTest = folio.newTestType<{ value: string }>();
// - Some special tests that require different arguments.
export const fooTest = folio.newTestType<{ foo: number }>();

// Environment with some test value.
class MockedEnv {
  async beforeEach() {
    return { value: 'some test value' };
  }
}

// Another environment that reads from file.
class FileEnv {
  constructor() {
    this.value = fs.readFileSync('data.txt', 'utf8');
  }
  async beforeEach() {
    return { value: this.value };
  }
}

// This environment provides foo.
class FooEnv {
  async beforeEach() {
    return { foo: 42 };
  }
}

// Now we can run tests in different configurations:
// - Generics tests with two different environments.
test.runWith(new MockedEnv());
test.runWith(new FileEnv());
// - Increased timeout for slow tests.
slowTest.runWith(new MockedEnv(), { timeout: 100000 });
// - Smoke tests without retries.
//   Adding a tag allows to run just the smoke tests with `npx folio --tag=smoke`.
smokeTest.runWith(new MockedEnv(), { retries: 0, tag: 'smoke' });
// - Special foo tests need a different environment.
fooTest.runWith(new FooEnv());

We can now use our test types to write tests:

// some.spec.ts

import { test, slowTest, smokeTest, fooTest } from './folio.config';

test('just a test', async ({ value }) => {
  // This test will be retried.
  expect(value).toBe('wrong value');
});

slowTest('does a lot', async ({ value }) => {
  for (let i = 0; i < 100000; i++)
    expect(value).toBe('some test value');
});

smokeTest('a smoke test', async ({ value }) => {
  // This test will not be retried.
  expect(value).toBe('some test value');
});

fooTest('a smoke test', async ({ foo }) => {
  // Note the different test arguments.
  expect(foo).toBe(42);
});

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