This is a testharness.js-based test.
[FAIL] Mixins work inside layers
  assert_equals: expected "rgb(0, 128, 0)" but got "rgb(0, 0, 0)"
[FAIL] Mixins work inside layers (anonymous)
  assert_equals: expected "rgb(0, 128, 0)" but got "rgb(0, 0, 0)"
[FAIL] Mixins in stronger layer wins
  assert_equals: expected "rgb(0, 128, 0)" but got "rgb(0, 0, 0)"
[FAIL] Mixins in stronger layer wins (source order matching layer order)
  assert_equals: expected "rgb(0, 128, 0)" but got "rgb(0, 0, 0)"
Harness: the test ran to completion.