SassMeister-input.scss

// ----
// Sass (v3.3.10)
// Compass (v1.0.0.alpha.20)
// ----

$base-path: "assets/" !default;

/**
 * Asset handler
 *
 * @param {String} $type
 * @param {String} $asset
 *
 * @requires {variable} base-path
 *
 * @return {String} Returns a `url()` function
 */
@function asset($type, $asset) {
  @return url($base-path + $type + '/' + $asset);
}

/**
 * Image helper
 *
 * @param {String} $image
 *
 * @requires {function} asset
 *
 * @return {String} Returns a `url()` function
 */
@function image($image) {
  @return asset('images', $image);
}

test {
  background: image('unicorn.jpg');
}

SassMeister-output.css

/**
 * Asset handler
 *
 * @param {String} $type
 * @param {String} $asset
 *
 * @requires {variable} base-path
 *
 * @return {String} Returns a `url()` function
 */
/**
 * Image helper
 *
 * @param {String} $image
 *
 * @requires {function} asset
 *
 * @return {String} Returns a `url()` function
 */
test {
  background: url("assets/images/unicorn.jpg");
}