0 30)`);
    test_valid_value(`color`, `lch(from lch(0.7 45 30 / none) l c h / alpha)`,                             `lch(0.7 45 30 / 0)`);

    // oklch()

    // Testing no modifications.
    test_valid_value(`color`, `oklch(from oklch(0.7 0.45 30) l c h)`, `oklch(0.7 0.45 30)`);
    test_valid_value(`color`, `oklch(from oklch(0.7 0.45 30) l c h / alpha)`, `oklch(0.7 0.45 30)`);
    test_valid_value(`color`, `oklch(from oklch(0.7 0.45 30 / 40%) l c h / alpha)`, `oklch(0.7 0.45 30 / 0.4)`);
    test_valid_v