-bezier(0, 0.7, 1, 1.3)");
test_valid_value("animation-timing-function", "cubic-bezier(calc(-2), calc(0.7 / 2), calc(1.5), calc(0))", "cubic-bezier(calc(-2), calc(0.35), calc(1.5), calc(0))");
test_valid_value("animation-timing-function", "cubic-bezier(0, sibling-index(), 1, sign(2em - 20px))");

test_valid_value("animation-timing-function", "steps(4, start)");
test_valid_value("animation-timing-function", "steps(2, end)", "steps(2)");
test_valid_value("animation-timing-function", "steps( 2, end )", "steps(