Status of this document:

JavaScript Testing Notes

There are multiple concerns in JavaScript testing: test execution, test assertion, and spying/mocking. Some libraries do all of them; some focus on just one.

Tools we'll likely use are highlighted.

• JSUnit
  • A port of JUnit to JavaScript
  • Does all the things.
  • Old - written before idiomatic JS testing was a thing, and not updated.

    "JsUnit is not actively developed or supported."

  • Supported internally at Google.
• Jasmine
  • The original native-to-JavaScript testing framework
  • Does all the things.
  • Popular among older projects.
  • Least modular popular option
    • @traviskaufman uses the example that mocking requestAnimationFrame is painful
• Ava
  • Test runner with optional assertion library
  • Doesn't pollute global namespace with test methods
  • Runs tests in parallel
  • Can export results to Test Anywhere Protocol for machine consumption
  • Written by @sindresorhus, a frequent collaborator of @addyo
  • Newer than the other popular options - likely in response to things they did less-well (like run tests in serial)
• Chai
  • Assertion library
  • Uses object tree format (e.g. expect(thing).to.equal(otherThing))
  • Popular among newer projects (usually paired with Mocha and Sinon)
• Sinon
  • Spy library
  • @traviskaufman contributes
• Expect
  • @mjackson got tired of needing separate dependencies for assertions and spies, so he wrote one library that includes both.
  • Assertion methods are in camel-case vs. in an object tree (eg. toBeEqual instead of to.equal)
• Mocha
  • Test runner, tracks which ones pass/fail
  • Popular with Chai and Karma
  • Runs tests in serial
• Karma
  • Test harness, opens a bunch of browsers and tracks which ones have problems
  • Written by Angular team
  • Popular paired with Chai, Mocha, and Sinon
• Tape
  • Does all the things.
  • Exports results in Test Anything Protocol, to be consumed by machines or formatted to be human readable by a separate tool.
  • Simpler/lower level than most options
• Jest
  • Built by Facebook to run Jasmine tests with automatically-mocked dependencies
  • A quick Google Search makes it look like this magic is a fragile as it sounds.
• Istanbul
  • Measures code coverage
  • That's all I know

TODO(appsforartists):

• Figure out and document the actual structure of this (e.g. npm run test will run ava which will in turn call __tests__/** in each package).
• Document how to add a test to go along with a new feature/bug fix.