Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

/* first test */

$small: nothing; // fallback for images not uploaded

@mixin testSmall($s: null) {
  @if ($s == nothing) {
    display: none
  } @else {
    background: transparent url(img) no-repeat 50% 50%;
    background-size: cover;
    padding-bottom: 94.85%;
  }
}
@include testSmall($small);

/* second test */

$small: any other value in the world; // link or value for uploaded image

@mixin testSmall($s: null) {
  @if ($s == nothing) {
    display: none
  } @else {
    background: transparent url(img) no-repeat 50% 50%;
    background-size: cover;
    padding-bottom: 94.85%;
  }
}
@include testSmall($small);

SassMeister-output.css

/* first test */
display: none;
/* second test */
background: transparent url(img) no-repeat 50% 50%;
background-size: cover;
padding-bottom: 94.85%;