Back to Repositories

Testing Template Package Resolution Implementation in facebook/create-react-app

This test suite validates the template installation package resolution functionality in Create React App. It ensures proper handling of various template naming patterns and versioning schemes for both default and custom templates.

Test Coverage Overview

The test suite provides comprehensive coverage of template package name resolution scenarios.

Default template resolution (cra-template)
TypeScript template variations
Version-specific template handling (@next)
Scoped package resolution (@iansu)
Remote template URL handling

Implementation Analysis

The testing approach utilizes Jest’s async/await pattern with promise resolution assertions. Each test case follows a consistent structure using expect().resolves.toBe() to verify the correct template package name transformation.

The implementation leverages Jest’s describe/it blocks for organized test grouping and clear test case isolation.

Technical Details

Testing Framework: Jest
Assertion Style: Promise resolution with .resolves
Test Structure: Modular describe/it blocks
Module Testing: getTemplateInstallPackage function
Asynchronous Testing: async/await pattern

Best Practices Demonstrated

The test suite exemplifies several testing best practices for Node.js module testing.

Consistent naming conventions for test cases
Proper async/await handling
Comprehensive edge case coverage
Clear test case isolation
Descriptive test case naming

facebook/create-react-app

packages/create-react-app/__tests__/getTemplateInstallPackage.test.js

            
/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

'use strict';

const { getTemplateInstallPackage } = require('../createReactApp');

describe('getTemplateInstallPackage', () => {
  it('no options gives cra-template', async () => {
    await expect(getTemplateInstallPackage()).resolves.toBe('cra-template');
  });

  it('cra-template gives cra-template', async () => {
    await expect(getTemplateInstallPackage('cra-template')).resolves.toBe(
      'cra-template'
    );
  });

  it('cra-template-typescript gives cra-template-typescript', async () => {
    await expect(
      getTemplateInstallPackage('cra-template-typescript')
    ).resolves.toBe('cra-template-typescript');
  });

  it('typescript gives cra-template-typescript', async () => {
    await expect(getTemplateInstallPackage('typescript')).resolves.toBe(
      'cra-template-typescript'
    );
  });

  it('typescript@next gives cra-template-typescript@next', async () => {
    await expect(getTemplateInstallPackage('typescript@next')).resolves.toBe(
      'cra-template-typescript@next'
    );
  });

  it('cra-template@next gives cra-template@next', async () => {
    await expect(getTemplateInstallPackage('cra-template@next')).resolves.toBe(
      'cra-template@next'
    );
  });

  it('cra-template-typescript@next gives cra-template-typescript@next', async () => {
    await expect(
      getTemplateInstallPackage('cra-template-typescript@next')
    ).resolves.toBe('cra-template-typescript@next');
  });

  it('@iansu gives @iansu/cra-template', async () => {
    await expect(getTemplateInstallPackage('@iansu')).resolves.toBe(
      '@iansu/cra-template'
    );
  });

  it('@iansu/cra-template gives @iansu/cra-template', async () => {
    await expect(
      getTemplateInstallPackage('@iansu/cra-template')
    ).resolves.toBe('@iansu/cra-template');
  });

  it('@iansu/cra-template@next gives @iansu/cra-template@next', async () => {
    await expect(
      getTemplateInstallPackage('@iansu/cra-template@next')
    ).resolves.toBe('@iansu/cra-template@next');
  });

  it('@iansu/cra-template-typescript@next gives @iansu/cra-template-typescript@next', async () => {
    await expect(
      getTemplateInstallPackage('@iansu/cra-template-typescript@next')
    ).resolves.toBe('@iansu/cra-template-typescript@next');
  });

  it('http://example.com/cra-template.tar.gz gives http://example.com/cra-template.tar.gz', async () => {
    await expect(
      getTemplateInstallPackage('http://example.com/cra-template.tar.gz')
    ).resolves.toBe('http://example.com/cra-template.tar.gz');
  });
});