The following animation test will fail. If you change the time of the first keyframe from 0ms to 1ms then it works.

import javafx.animation.*;

var done: Boolean = false;

var t = Timeline {
    keyFrames: [
        KeyFrame {
            time: 0ms
            action: function() { done = true; }
        }
    ]
};
t.playFromStart();

var tCheck = Timeline {
    keyFrames: [
        KeyFrame {
            time: 1s
            action: function() {
                if (done) {
                    println("PASSED");
                } else {
                    println("FAILED: Timeline with 0ms KeyFrame not run");
                }
            }
        }
    ]
};
tCheck.playFromStart();