given:
        def action1 = {
            instant.action1Start
            thread.block()
            instant.action1End
        }
        def action2 = {
            instant.action2Start
        }

        when:
        start {
            synchronizer.runNow(action1)
        }
        async {
            thread.blockUntil.action1Start
            synchronizer.runNow(action2)