less.js/test/rhino/test-header.js

function initRhinoTest() {
    process = { title: 'dummy' };

    less.tree.functions.add = function (a, b) {
        return new(less.tree.Dimension)(a.value + b.value);
    };
    less.tree.functions.increment = function (a) {
        return new(less.tree.Dimension)(a.value + 1);
    };
    less.tree.functions._color = function (str) {
        if (str.value === 'evil red') { return new(less.tree.Color)('600'); }
    };
}

initRhinoTest();