<!doctype html>
<meta charset="utf-8">
<title>Joint session history should not override parent's state.</title>
<meta name="timeout" content="long">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<body>
<iframe id="frame" src="about:blank"></iframe>
<script>
async_test(function(t) {
    // Setup.
    var initialState = {foo: 'bar'};
    var newStateFromChild = {foo: 'baz'};
    var child = document.getElementById("frame");

    // Child's initial state should be a default empty state.
    assert_equals(child.contentWindow.history.state, null);

    // Perform navigation in the top-level container to set the state.
    window.history.pushState(initialState, 'title');

    // Validate initial state was properly set.
    assert_object_equals(window.history.state, initialState);

    child.onload = t.step_func_done(() => {
        // Child's initial state should be `null`.
        assert_equals(child.contentWindow.history.state, null);

        // Navigate in the child.
        child.contentWindow.history.pushState(newStateFromChild, 'title');

        // Child's state should now equal the new state.
        assert_object_equals(child.contentWindow.history.state, newStateFromChild);
        // Parent's state should still be preserved, having exactly the same state as it
        // had before parent navigated.
        assert_object_equals(window.history.state, initialState);
    })
    child.src = "joint-session-history-filler.html";
});
</script>
</body>
