src/third_party/mozjs-45/js/src/jit-test/tests/basic/testNativeSetter.js

function testNativeSetter() {
    var re = /foo/;
    var N = 19;
    for (var i = 0; i < N; i++)
        re.lastIndex = i;
    assertEq(re.lastIndex, N - 1);
}
testNativeSetter();