5px 6px black',
  to: '-15px -10px 25px -4px',
}, [
  {at: -0.3, expect: 'rgb(0, 0, 0) 24px 16px 0px 9px'},
  {at: 0, expect: 'rgb(0, 0, 0) 15px 10px 5px 6px'},
  {at: 0.3, expect: 'rgb(0, 38, 0) 6px 4px 11px 3px'},
  {at: 0.6, expect: 'rgb(0, 77, 0) -3px -2px 17px 0px'},
  {at: 1, expect: 'rgb(0, 128, 0) -15px -10px 25px -4px'},
  {at: 1.5, expect: 'rgb(0, 192, 0) -30px -20px 35px -9px'},
]);

test_interpolation({
  property: 'box-shadow',
  from: '10px 10px 10px 10px black',
  to: '10px 10px 10px 10px cur