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Testing File Path Ignore Patterns in Create-React-App

This test suite validates the file ignoring functionality in Create React App’s development utilities, specifically focusing on how different file paths are handled for watch exclusions. The tests ensure proper handling of node_modules and source directory paths.

Test Coverage Overview

The test suite provides comprehensive coverage of the ignoredFiles utility, examining various file path scenarios.

Key areas tested include:

Regular file path handling
Node modules detection
Source directory path handling
Nested node_modules within source directories
Path prefix matching

Implementation Analysis

The testing approach uses Jest’s describe/it pattern to organize related test cases logically. Each test case follows a consistent structure of setting up a source path, testing file paths against the ignore regex, and asserting expected outcomes using Jest’s expect statements.

The implementation leverages Jest’s built-in assertion library and employs clear test case isolation.

Technical Details

Testing tools and configuration:

Jest as the testing framework
Regular expressions for path matching
Mock file paths for various scenarios
Strict mode JavaScript
MIT licensed test implementation

Best Practices Demonstrated

The test suite exemplifies several testing best practices in its implementation.

Notable practices include:

Descriptive test case naming
Isolated test scenarios
Consistent test structure
Clear expected vs actual assertions
Comprehensive edge case coverage

facebook/create-react-app

packages/react-dev-utils/__tests__/ignoredFiles.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 ignoredFiles = require('../ignoredFiles');

describe('ignore watch files regex', () => {
  it('normal file', () => {
    const appSrc = '/root/src/';
    const isIgnored = ignoredFiles(appSrc).test('/foo');
    const isIgnoredInSrc = ignoredFiles(appSrc).test('/root/src/foo');

    expect(isIgnored).toBe(false);
    expect(isIgnoredInSrc).toBe(false);
  });

  it('node modules', () => {
    const appSrc = '/root/src/';
    const isIgnored = ignoredFiles(appSrc).test('/root/node_modules/foo');

    expect(isIgnored).toBe(true);
  });

  it('node modules inside source directory', () => {
    const appSrc = '/root/src/';
    const isIgnored = ignoredFiles(appSrc).test('/root/src/node_modules/foo');
    const isIgnoredMoreThanOneLevel = ignoredFiles(appSrc).test(
      '/root/src/bar/node_modules/foo'
    );

    expect(isIgnored).toBe(false);
    expect(isIgnoredMoreThanOneLevel).toBe(false);
  });

  it('path contains source directory', () => {
    const appSrc = '/root/src/';
    const isIgnored = ignoredFiles(appSrc).test(
      '/bar/root/src/node_modules/foo'
    );

    expect(isIgnored).toBe(true);
  });

  it('path starts with source directory', () => {
    const appSrc = '/root/src/';
    const isIgnored = ignoredFiles(appSrc).test('/root/src2/node_modules/foo');

    expect(isIgnored).toBe(true);
  });
});