use es2015 syntax in mocha tests

[marcobiedermann]

use babel to use es2015 syntax in mocha tests

• use import instead of require
• use fat arrow => function instead of function() {} callback
• use and let and const instead of var
• use template stings instead of string concatenation

[chrislaughlin]

👍

[paulirish]

Thanks for writing the PR.

I'd be interested in accepting this if its not dependent on babel. In my experience adding transpilation into your test runner makes debugging fairly painful.

If you want to confirm with node.green that all this stuff works in stable node 4.4 then let's just rip out the babel bit and ship it.

[marcobiedermann]

@paulirish Thanks Paul for your comment.
As far as I know there is no other way than using a transpiler like Babel to use import state in JavaScript.
All other features: arrow functions, let, const and template strings are supported in Node 4.4+
The only solution dropping Babel would be to stick with require instead of import.

Do you know another way to get around this issue?

[marcobiedermann]

@paulirish
I've merged the current master into my PR to keep it up to date.
I've also noticed that you already include Babel.js so we are good with using import in tests.