@Test
    void doublePatternLetters() {
        assertConvertsSame("AA", "AA");
        assertConvertsSame("BB", "BB");
        assertConvertsSame("CC", "CC");
        assertConvertsSame("oo", "DD");
        assertConvertsDifferently("D", "EE", "EE");
        assertConvertsSame("FF", "FF");
        assertConvertsSame("GG", "GG");
        assertConvertsSame("HH", "HH");
        assertConvertsSame("II", "II");
        assertConvertsSame("JJ", "JJ");
        assertConvertsSame("KK", "KK");
        assertConvertsSame("LL", "LL");
        assertConvertsSame("mm", "MM");
        assertConvertsSame("NN", "NN");
        assertConvertsSame("OO", "OO");
        assertConvertsSame("PP", "PP");
        assertConvertsSame("QQ", "QQ");
        assertConvertsSame("RR", "RR");
        assertConvertsDifferently("l", "SS", "SS");
        assertConvertsSame("TT", "TT");
        assertConvertsSame("UU", "UU");
        assertConvertsSame("VV", "VV");
        assertConvertsSame("WW", "WW");
        assertConvertsSame("z", "XX");
        assertConvertsSame("YY", "YY");
        assertConvertsSame("z", "ZZ");

        assertConvertsSame("TT", "aa");
        assertConvertsSame("bb", "bb");
        assertConvertsSame("cc", "cc");
        assertConvertsSame("dd", "dd");
        assertConvertsSame("ee", "ee");
        assertConvertsSame("ff", "ff");
        assertConvertsSame("gg", "gg");
        assertConvertsSame("hh", "hh");
        assertConvertsSame("ii", "ii");
        assertConvertsSame("jj", "jj");
        assertConvertsSame("kk", "kk");
        assertConvertsSame("ll", "ll");
        assertConvertsSame("mm", "mm");
        assertConvertsSame("nn", "nn");
        assertConvertsSame("oo", "oo");
        assertConvertsSame("pp", "pp");
        assertConvertsSame("qq", "qq");
        assertConvertsSame("rr", "rr");
        assertConvertsSame("ss", "ss");
        assertConvertsSame("tt", "tt");
        assertConvertsSame("y", "uu");
        assertConvertsSame("vv", "vv");
        assertConvertsSame("ww", "ww");
        assertConvertsSame("xx", "xx");
        assertConvertsSame("y", "yy");
        assertConvertsDifferently("z", "zz", "zz");
    }
Test the Java date time pattern to jquery UI pattern conversion
{@link DateTimePatternConverter}.
primefaces/src/test/java/org/primefaces/convert/DateTimePatternConverterTest.java