I'm all the way down to test 28. Where the function declared is var id = function (id) { return id; }
But when I print the given function I actually get function id(_id) { return _id; }
The argument passed into the defaultArguments is { id: 'test' }
My first question is: Is there a special meaning to parameters prefixed with _?

Second, when I work around this test by ignoring any _ prefix. The second test which calls the exact same function, and passes the exact same argument into defaultArguments expects the method not to return a default.
Is this a broken test or am I missing something?

My test output with some logging:
var id = function (id) { return id; }

function id(_id) {
return _id;
}
Args: { id: 'test' }
Test Passed: Value == test

function id(_id) {
return _id;
}
Args: { id: 'test' }
defaultArguments(id,{id:"test"})(undefined) - Expected: undefined, instead got: test