How does Mocha know that done was specified?
mocha.js, node.js, tdd
Solution
It uses the `.length` property on the test function.
To illustrate, try this in the Node REPL:
> (function() {}).length
0
> (function(done) {}).length
1
Here's the actual line in the source where this check happens:
this.async = fn && fn.length;
Problem
If I write an asynchronous test using Mocha, all I need to do is to specify the done parameter on the test function: ``` test('foo', function (done) {...}); ``` My question is: How does Mocha know whether done was given? The definition of the test function should be something such as ``` function test(title, fn) {...}; ``` How does Mocha check fn?