The failing test cases:

src/test/java/org/joda/time/TestLocalDateTime_Constructors.java:112-118
    public void testFactory_fromCalendarFields_beforeYearZero1() throws Exception {
        GregorianCalendar cal = new GregorianCalendar(1, 1, 3, 4, 5, 6);
        cal.set(Calendar.ERA, GregorianCalendar.BC);
        cal.set(Calendar.MILLISECOND, 7);
        LocalDateTime expected = new LocalDateTime(0, 2, 3, 4, 5, 6, 7);
        assertEquals(expected, LocalDateTime.fromCalendarFields(cal));        // <-- TC fails here
    }
src/test/java/org/joda/time/TestLocalDateTime_Constructors.java:120-126
    public void testFactory_fromCalendarFields_beforeYearZero3() throws Exception {
        GregorianCalendar cal = new GregorianCalendar(3, 1, 3, 4, 5, 6);
        cal.set(Calendar.ERA, GregorianCalendar.BC);
        cal.set(Calendar.MILLISECOND, 7);
        LocalDateTime expected = new LocalDateTime(-2, 2, 3, 4, 5, 6, 7);
        assertEquals(expected, LocalDateTime.fromCalendarFields(cal));        // <-- TC fails here
    }
src/test/java/org/joda/time/TestLocalDateTime_Constructors.java:150-156
    public void testFactory_fromDateFields_beforeYearZero1() throws Exception {
        GregorianCalendar cal = new GregorianCalendar(1, 1, 3, 4, 5, 6);
        cal.set(Calendar.ERA, GregorianCalendar.BC);
        cal.set(Calendar.MILLISECOND, 7);
        LocalDateTime expected = new LocalDateTime(0, 2, 3, 4, 5, 6, 7);
        assertEquals(expected, LocalDateTime.fromDateFields(cal.getTime()));  // <-- TC fails here
    }
src/test/java/org/joda/time/TestLocalDateTime_Constructors.java:158-164
    public void testFactory_fromDateFields_beforeYearZero3() throws Exception {
        GregorianCalendar cal = new GregorianCalendar(3, 1, 3, 4, 5, 6);
        cal.set(Calendar.ERA, GregorianCalendar.BC);
        cal.set(Calendar.MILLISECOND, 7);
        LocalDateTime expected = new LocalDateTime(-2, 2, 3, 4, 5, 6, 7);
        assertEquals(expected, LocalDateTime.fromDateFields(cal.getTime()));  // <-- TC fails here
    }
src/test/java/org/joda/time/TestLocalDate_Constructors.java:104-110
    public void testFactory_fromCalendarFields_beforeYearZero1() throws Exception {
        GregorianCalendar cal = new GregorianCalendar(1, 1, 3, 4, 5, 6);
        cal.set(Calendar.ERA, GregorianCalendar.BC);
        cal.set(Calendar.MILLISECOND, 7);
        LocalDate expected = new LocalDate(0, 2, 3);
        assertEquals(expected, LocalDate.fromCalendarFields(cal));            // <-- TC fails here
    }
src/test/java/org/joda/time/TestLocalDate_Constructors.java:112-118
    public void testFactory_fromCalendarFields_beforeYearZero3() throws Exception {
        GregorianCalendar cal = new GregorianCalendar(3, 1, 3, 4, 5, 6);
        cal.set(Calendar.ERA, GregorianCalendar.BC);
        cal.set(Calendar.MILLISECOND, 7);
        LocalDate expected = new LocalDate(-2, 2, 3);
        assertEquals(expected, LocalDate.fromCalendarFields(cal));            // <-- TC fails here
    }
src/test/java/org/joda/time/TestLocalDate_Constructors.java:142-148
    public void testFactory_fromDateFields_beforeYearZero1() throws Exception {
        GregorianCalendar cal = new GregorianCalendar(1, 1, 3, 4, 5, 6);
        cal.set(Calendar.ERA, GregorianCalendar.BC);
        cal.set(Calendar.MILLISECOND, 7);
        LocalDate expected = new LocalDate(0, 2, 3);
        assertEquals(expected, LocalDate.fromDateFields(cal.getTime()));      // <-- TC fails here
    }
src/test/java/org/joda/time/TestLocalDate_Constructors.java:150-156
    public void testFactory_fromDateFields_beforeYearZero3() throws Exception {
        GregorianCalendar cal = new GregorianCalendar(3, 1, 3, 4, 5, 6);
        cal.set(Calendar.ERA, GregorianCalendar.BC);
        cal.set(Calendar.MILLISECOND, 7);
        LocalDate expected = new LocalDate(-2, 2, 3);
        assertEquals(expected, LocalDate.fromDateFields(cal.getTime()));      // <-- TC fails here
    }

The faulty code:

Line is covered but NOT in slice
Line is covered and in slice
Line is in slice but NOT covered
src/main/java/org/joda/time/LocalDateTime.java:195-209
    public static LocalDateTime fromCalendarFields(Calendar calendar) {
        if (calendar == null) {
            throw new IllegalArgumentException("The calendar must not be null");
        }
        int yearOfEra = calendar.get(Calendar.YEAR);
        return new LocalDateTime(                                             // <-- statement includes bug
            yearOfEra,                                                        // <-- BUG!!
            calendar.get(Calendar.MONTH) + 1,
            calendar.get(Calendar.DAY_OF_MONTH),
            calendar.get(Calendar.HOUR_OF_DAY),
            calendar.get(Calendar.MINUTE),
            calendar.get(Calendar.SECOND),
            calendar.get(Calendar.MILLISECOND)
        );
    }
src/main/java/org/joda/time/LocalDateTime.java:611-616
    public boolean isSupported(DateTimeFieldType type) {
        if (type == null) {
            return false;
        }
        return type.getField(getChronology()).isSupported();
    }
src/main/java/org/joda/time/LocalDate.java:206-216
    public static LocalDate fromCalendarFields(Calendar calendar) {
        if (calendar == null) {
            throw new IllegalArgumentException("The calendar must not be null");
        }
        int yearOfEra = calendar.get(Calendar.YEAR);
        return new LocalDate(                                                 // <-- statement includes bug
            yearOfEra,                                                        // <-- BUG!!
            calendar.get(Calendar.MONTH) + 1,
            calendar.get(Calendar.DAY_OF_MONTH)
        );
    }