ES6 Methods and the Verse Test Framework

You’re probably familiar with ECMAScript 6’s method syntax:

let obj = {
  foo() {
    return 'hello from foo'
  },

  bar() {
    return 'hello from bar'
  }
}

This is just shorthand for

let obj = {
  foo: function () {
    return 'hello from foo'
  },

  bar: function () {
    return 'hello from bar'
  }
}

You’re also probably aware that object keys can contain arbitrary characters if you put them in quotes. When written this way, JavaScript object literals look a lot like JSON:

let obj = {
  "a method name with spaces": function () {
    return 'whoa'
  }
}

But did you know… that you can combine these things?

let obj = {
  'a method name with spaces'() {
    return 'whoa'
  }
}

Craziness!

This turns out to work really nicely with the test framework I’d envisioned for Verse. I wanted to avoid the verbosity of frameworks like Jest and Jasmine and make tests as syntactically minimal as possible. I hoped that by minimizing the activation energy required for testing, I might encourage people to write more tests.

To that end, tests are simply globally define()d functions whose names start with "test ".

define({
  'test math works'() {
    check(1 + 1, equals, 2)
  },

  'test math still works'() {
    check(2 + 2, equals, 4)
  }
})

Isn’t that nice?

We can take this even further with yet another ES6 feature: dynamic keys in object literals. In modern browsers, you can do this:

let obj = {
  ['foo' + (1 + 2 + 3)]: function() {
    return 'you called foo6()'
  }
}

And, you guessed it, this works with method syntax too:

let obj = {
  ['foo' + (1 + 2 + 3)]() {
    return 'you called foo6()'
  }
}

This means that if you have a test with an awkwardly long name, you can just break it into multiple lines:

define({
  ['a test with a really really long description that ' +
   'needs multiple lines to properly express itself']() {
    check(1 + 1, equals, 2)
  }
})

The Verse test framework isn’t ready yet, but soon you’ll be able to write tests like this, right in your browser. Until then, you can check out this demo, or try your hand at writing Verse code at druidic.github.io

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