@codemod-utils/tests

Utilities for tests

What is it?

@codemod-utils/tests helps you write fixture-driven tests. The tests execute fast and are "dependency-free."

API

test

The test method comes from @sondr3/minitest.

import { test } from '@codemod-utils/tests';

test('Some method', function () {
  // ...
});

You can append .only() to run a subset of tests. This may be useful for debugging.

test('Some method', function () {
  // ...
}).only();

Note, test files must have the extension .test.ts or .test.js. Check the main tutorial for conventions around tests.

assert

The assert object comes from Node.js.

import { assert, test } from '@codemod-utils/tests';

import { createOptions } from '../../../src/steps/index.js';
import {
  codemodOptions,
  options,
} from '../../helpers/shared-test-setups/sample-project.js';

test('steps | create-options > sample-project', function () {
  assert.deepStrictEqual(createOptions(codemodOptions), options);
});

Make strong assertions whenever possible, using methods such as assert.deepStrictEqual(), assert.strictEqual(), and assert.throws(). Weak assertions like assert.match() and assert.ok(), which create a "room for interpretation" and can make tests pass when they shouldn't (false negatives), should be avoided.

• assert.deepStrictEqual() - check "complex" data structures (array, object, Map)
• assert.strictEqual() - check "simple" data structures (Boolean, number, string)
• assert.throws() - check error messages

convertFixtureToJson, loadFixture, assertFixture

Use these methods to document how the codemod updates folders and files.

/* tests/fixtures/sample-project/index.ts */
import { convertFixtureToJson } from '@codemod-utils/tests';

const inputProject = convertFixtureToJson('sample-project/input');
const outputProject = convertFixtureToJson('sample-project/output');

export { inputProject, outputProject };

/* tests/index/sample-project.test.ts */
import { assertFixture, loadFixture, test } from '@codemod-utils/tests';

import { runCodemod } from '../../src/index.js';
import {
  inputProject,
  outputProject,
} from '../fixtures/sample-project/index.js';
import { codemodOptions } from '../helpers/shared-test-setups/sample-project.js';

test('index > sample-project', function () {
  loadFixture(inputProject, codemodOptions);

  runCodemod(codemodOptions);

  assertFixture(outputProject, codemodOptions);

  // Check idempotence
  runCodemod(codemodOptions);

  assertFixture(outputProject, codemodOptions);
});

In the example above (an "acceptance" test), inputProject and outputProject were derived from folders and files that actually exist. At times, it may be easier to define inputProject and outputProject in the test file. This is often the case for "integration" tests, i.e. tests for a single step. Maybe only a few types of files need to be checked, or the file content can be empty because it plays no role in the step.

Compatibility

• Node.js v18 or above

Contributing

See the Contributing guide for details.

License

This project is licensed under the MIT License.