Nodejs Testing Tips

How to setup tests in Nodejs project?

• Use a ./test folder in the project root to hold all tests
• Install and use esm to support import syntax in Nodejs for cleaner code
• For integration test, install dependencies like better-sqlite3 and node-sqlite3 to test database interactions
• Tests can use helper functions from ./test/support/helper.js
• Organize tests by feature in separate files, like ./test/featureA.test.js

How to write integration tests using databases in Nodejs?

• Use an in-memory database like better-sqlite3 to avoid test polution
• Write helper functions to setup and seed the in-memory database for each test module
• Use beforeEach and afterEach to setup/cleanup database for each test case

How to test CLI commands in Nodejs?

• Put each command test case in a separate subfolder under ./test
• Each subfolder contains:
  • cmd - The CLI command to run
  • input - Input passed to the CLI
  • expected.stdout - Expected standard output
  • expected.stderr - Expected standard error
• Use child_process.exec in test file to execute the cmd
• Assert exitCode, stdout, stderr with expected values

// Execute CLI command
var exec = require('child_process').exec; 

exec('bash cmd', {cwd: dir}, function(error, stdout, stderr) {
  // Assert exitCode, stdout, stderr
});

How to turn JS code using require to import for tests?

• Use esm to transpile import syntax on the fly
• Alternative is to use babel to transpile entire test codebase
• Keep production codebase untouched to avoid breaking changes

// Install esm
npm install --save-dev esm 

// Use esm to run tests
npm test -- --require esm 

ref:

• https://github.com/mapbox/node-sqlite3
• https://github.com/JoshuaWise/better-sqlite3
• https://www.npmjs.com/package/esm