@mixin test($one: 'foo', $two: 'bar') {
	one: $one;
	two: $two;
}

default {
	@include test();
}

one {
	@include test('one');
}

two {
	@include test($two: 'two');
}

both {
	@include test('one', 'two');
}

whitespace {
  @include test ('one', 'two');
}

parens {
  @include test('one', rgb(255, 255, 255) );
}