 to: "none"
      });

      test_no_interpolation({
        property: 'grid-template-columns',
        from: "none",
        to: "20px 30px"
      });

      // Exercise <explicit-track-list>
      test_interpolation({
        property: 'grid-template-columns',
        from: "10px 20px 30px",
        to: "20px 30px 40px"
      }, [
        {at: -1, expect: "0px 10px 20px"},
        {at: 0, expect: "10px 20px 30px"},
        {at: 0.4, expect: "14px 24px 34px"},
        {at: 0.6, expect: "16px 26px 36px"},
 