assertTrue(output.contains("event: test"));
        assertTrue(output.contains("inner"));
        assertTrue(output.contains("value"));
    }

    @Test
    public void test_sendSseEvent_listData() {
        final StringWriter stringWriter = new StringWriter();
        final PrintWriter writer = new PrintWriter(stringWriter);

        final List<String> items = List.of("item1", "item2", "item3");