@Test
    void duplicateHtmlElements() throws IOException {
        writer.startElement("HTML", null);
        verify(wrappedWriter).startElement("HTML", null);


        FacesException exception = assertThrows(FacesException.class, () -> {
            writer.startElement("HtmL", null);
        });
        assertEquals("Duplicate <html> elements were found in the response.", exception.getMessage());
    }
https://github.com/primefaces/primefaces/issues/10845
primefaces/src/test/java/org/primefaces/application/resource/MoveScriptsToBottomResponseWriterTest.java