Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.13)
// Compass (v1.0.3)
// ----

$images-base-path: 'test/';

@mixin retinaBg($path) {
  
  background-image: url($images-base-path + $path +'.png');
  
  @media  only screen and (min-device-pixel-ratio: 2), 
        only screen and (min-resolution: 192dpi) {
    background-image: url($images-base-path + $path +'@2x.png');
  }

}

.foo{
  @include retinaBg('/icons/options/sms');
}

SassMeister-output.css

.foo {
  background-image: url(test//icons/options/sms.png?1431340934);
}
@media only screen and (min-device-pixel-ratio: 2), only screen and (min-resolution: 192dpi) {
  .foo {
    background-image: url(test//icons/options/sms@2x.png?1431340934);
  }
}