diff --git a/tests/Cmixin/BusinessDayTest.php b/tests/Cmixin/BusinessDayTest.php
index 53b9d1a..c00b3b5 100644
--- a/tests/Cmixin/BusinessDayTest.php
+++ b/tests/Cmixin/BusinessDayTest.php
@@ -230,6 +230,33 @@ public function testIfRuleWithHijriCalendar()
 
         self::assertSame(['hari-raya-puasa' => '2020-05-25 00:00:00'], $year(2020));
         self::assertSame(['hari-raya-puasa' => '2021-05-13 00:00:00'], $year(2021));
+
+        $carbon::resetHolidays();
+        $carbon::setHolidays('custom', [
+            'hari-raya-haji' => '= 10 dhu al-hijjah if sunday then next monday',
+        ]);
+        $carbon::setHolidaysRegion('custom');
+        $year = static function (int $year) use ($carbon) {
+            return array_map('strval', $carbon::getYearHolidays($year));
+        };
+
+        self::assertSame(['hari-raya-haji' => '2000-03-16 00:00:00'], $year(2000));
+        self::assertSame(['hari-raya-haji' => '2001-03-06 00:00:00'], $year(2001));
+        self::assertSame(['hari-raya-haji' => '2002-02-23 00:00:00'], $year(2002));
+        self::assertSame(['hari-raya-haji' => '2003-02-12 00:00:00'], $year(2003));
+        self::assertSame(['hari-raya-haji' => '2004-02-02 00:00:00'], $year(2004));
+        self::assertSame(['hari-raya-haji' => '2005-01-21 00:00:00'], $year(2005));
+        self::assertSame([
+            'hari-raya-haji'      => '2006-01-10 00:00:00',
+            'hari-raya-haji-oc-2' => '2006-12-31 00:00:00',
+        ], $year(2006));
+        self::assertSame(['hari-raya-haji' => '2009-11-28 00:00:00'], $year(2009));
+        self::assertSame(['hari-raya-haji' => '2010-11-17 00:00:00'], $year(2010));
+        self::assertSame(['hari-raya-haji' => '2011-11-07 00:00:00'], $year(2011));
+        self::assertSame(['hari-raya-haji' => '2021-07-20 00:00:00'], $year(2021));
+        self::assertSame(['hari-raya-haji' => '2022-07-11 00:00:00'], $year(2022));
+        self::assertSame(['hari-raya-haji' => '2023-06-29 00:00:00'], $year(2023));
+        self::assertSame(['hari-raya-haji' => '2024-06-17 00:00:00'], $year(2024));
     }
 
     public function testCaseInsensitivity()
diff --git a/tests/Cmixin/Calendar/HijriCalendarTest.php b/tests/Cmixin/Calendar/HijriCalendarTest.php
new file mode 100644
index 0000000..baba8fd
--- /dev/null
+++ b/tests/Cmixin/Calendar/HijriCalendarTest.php
@@ -0,0 +1,30 @@
+<?php
+
+namespace Tests\Cmixin\Calendar;
+
+use Cmixin\BusinessDay\Calendar\HijriCalendar;
+use PHPUnit\Framework\TestCase;
+
+class HijriCalendarTest extends TestCase
+{
+    /** @dataProvider getDates */
+    public function testHolidaysSpecificDates(string $hijri, string $gregorian): void
+    {
+        $calendar = new HijriCalendar();
+        [$year, $month, $day] = explode('-', $hijri);
+        $date = $calendar->getDate($year, $month, $day);
+
+        self::assertSame($gregorian, implode('-', $date));
+    }
+
+    public static function getDates(): array
+    {
+        $tests = [
+            ['1428-12-10', '2007-12-20'],
+            ['1429-12-10', '2008-12-9'], // some converters give 2008-12-8
+            ['1430-12-10', '2009-11-28'], // some converters give 2009-11-27
+        ];
+
+        return array_combine(array_column($tests, 0), $tests);
+    }
+}