  "animationSequence.children.length");
test(function() {assert_equals(animationSequence.children[0], sibling)},
     "First child should be 'sibling'");
test(function() {assert_equals(animationSequence.children[1], child)},
     "Second child should be 'child'");
test(function() {assert_equals(sibling.startTime, 0.0)},
     "Start time of 'sibling'");
test(function() {assert_equals(child.startTime, 1.0)},
     "Start time of 'child'");

// Test that TimedItem.clear() updates both parent and children.
anima