Back to Repositories

Testing Environment Configuration Detection in Parcel

This test suite validates the Environment creation functionality in Parcel, focusing on context detection and configuration defaults. It ensures proper environment initialization for both browser and Node.js contexts with appropriate engine settings and build configurations.

Test Coverage Overview

The test suite provides comprehensive coverage of environment creation scenarios in Parcel.

Default environment configuration validation
Node.js context detection and configuration
Browser context detection and configuration
Engine defaults for both Node.js and browser environments

Implementation Analysis

The testing approach uses Jest’s describe/it pattern with Node’s assert module for assertions. Tests verify environment object creation through the createEnvironment function, checking object structure and property assignments.

Assertion-based verification of configuration objects
Deep equality comparisons for complex objects
Isolated test cases for different environment contexts

Technical Details

Testing Framework: Jest
Assertion Library: Node.js assert module
Flow type checking with strict-local mode
Environment creation utility from ‘../src/Environment’
Deep object comparison testing

Best Practices Demonstrated

The test suite exemplifies strong testing practices through clear organization and comprehensive coverage. Each test case focuses on a specific aspect of environment creation, with explicit assertions and well-structured test scenarios.

Isolated test cases for different configurations
Consistent testing patterns across scenarios
Complete object verification
Clear test case descriptions

parcel-bundler/parcel

packages/core/core/test/Environment.test.js

            
// @flow strict-local

import assert from 'assert';
import {createEnvironment} from '../src/Environment';

describe('Environment', () => {
  it('assigns a default environment with nothing passed', () => {
    assert.deepEqual(createEnvironment(), {
      id: 'c242f987e3544367',
      context: 'browser',
      engines: {
        browsers: ['> 0.25%'],
      },
      includeNodeModules: true,
      outputFormat: 'global',
      isLibrary: false,
      shouldOptimize: false,
      shouldScopeHoist: false,
      sourceMap: undefined,
      loc: undefined,
      sourceType: 'module',
    });
  });

  it('assigns a node context if a node engine is given', () => {
    assert.deepEqual(createEnvironment({engines: {node: '>= 10.0.0'}}), {
      id: '69e0ab7220ee8f7a',
      context: 'node',
      engines: {
        node: '>= 10.0.0',
      },
      includeNodeModules: false,
      outputFormat: 'commonjs',
      isLibrary: false,
      shouldOptimize: false,
      shouldScopeHoist: false,
      sourceMap: undefined,
      loc: undefined,
      sourceType: 'module',
    });
  });

  it('assigns a browser context if browser engines are given', () => {
    assert.deepEqual(
      createEnvironment({engines: {browsers: ['last 1 version']}}),
      {
        id: '4b5c9005af8c5b19',
        context: 'browser',
        engines: {
          browsers: ['last 1 version'],
        },
        includeNodeModules: true,
        outputFormat: 'global',
        isLibrary: false,
        shouldOptimize: false,
        shouldScopeHoist: false,
        sourceMap: undefined,
        loc: undefined,
        sourceType: 'module',
      },
    );
  });

  it('assigns default engines for node', () => {
    assert.deepEqual(createEnvironment({context: 'node'}), {
      id: 'b9b60fc7dcc0ae9c',
      context: 'node',
      engines: {
        node: '>= 18.0.0',
      },
      includeNodeModules: false,
      outputFormat: 'commonjs',
      isLibrary: false,
      shouldOptimize: false,
      shouldScopeHoist: false,
      sourceMap: undefined,
      loc: undefined,
      sourceType: 'module',
    });
  });

  it('assigns default engines for browsers', () => {
    assert.deepEqual(createEnvironment({context: 'browser'}), {
      id: 'c242f987e3544367',
      context: 'browser',
      engines: {
        browsers: ['> 0.25%'],
      },
      includeNodeModules: true,
      outputFormat: 'global',
      isLibrary: false,
      shouldOptimize: false,
      shouldScopeHoist: false,
      sourceMap: undefined,
      loc: undefined,
      sourceType: 'module',
    });
  });
});