diff --git a/.phive/phars.xml b/.phive/phars.xml
index bca34b9..1234f00 100644
--- a/.phive/phars.xml
+++ b/.phive/phars.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <phive xmlns="https://phar.io/phive">
-  <phar name="phpstan" version="1.12.3" installed="1.12.3" location="./tools/phpstan" copy="false"/>
+  <phar name="phpstan" version="2.0.1" installed="2.0.1" location="./tools/phpstan" copy="false"/>
   <phar name="psalm" version="5.26.1" installed="5.26.1" location="./tools/psalm" copy="false"/>
 </phive>
\ No newline at end of file
diff --git a/phpstan.neon b/phpstan.neon
index 8c2eb0d..ff6d291 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -2,6 +2,9 @@ parameters:
     paths:
       - src
       - tests/TestCase
-    level: 5
+    level: 8
     bootstrapFiles:
       - tests/bootstrap.php
+    ignoreErrors:
+        -
+            identifier: missingType.iterableValue
diff --git a/src/Scheduler/Scheduler.php b/src/Scheduler/Scheduler.php
index 73739d4..ff1dcbb 100644
--- a/src/Scheduler/Scheduler.php
+++ b/src/Scheduler/Scheduler.php
@@ -62,7 +62,11 @@ public function execute(string|callable $command, array $args = []): Event
         }
 
         try {
-            $commandObj = $this->container->get($command);
+            if ($this->container !== null) {
+                $commandObj = $this->container->get($command);
+            } elseif (class_exists($command)) {
+                $commandObj = new $command();
+            }
         } catch (ContainerExceptionInterface | NotFoundExceptionInterface $ex) {
             if (class_exists($command)) {
                 $commandObj = new $command();
diff --git a/src/Scheduler/Traits/FrequenciesTrait.php b/src/Scheduler/Traits/FrequenciesTrait.php
index 750a740..cbe2ff8 100644
--- a/src/Scheduler/Traits/FrequenciesTrait.php
+++ b/src/Scheduler/Traits/FrequenciesTrait.php
@@ -328,7 +328,7 @@ public function days(int|string|array $days): self
      */
     protected function spliceIntoPosition(int $position, mixed $value): self
     {
-        $segments = preg_split("/\s+/", $this->expression);
+        $segments = preg_split("/\s+/", $this->expression) ?: [];
 
         $segments[$position - 1] = $value;
 
diff --git a/tests/TestCase/Scheduler/EventTest.php b/tests/TestCase/Scheduler/EventTest.php
index ba9ac80..f72c6dc 100644
--- a/tests/TestCase/Scheduler/EventTest.php
+++ b/tests/TestCase/Scheduler/EventTest.php
@@ -26,53 +26,53 @@ public function testIsDue(): void
         Chronos::setTestNow('now');
     }
 
-    public function testEveryMinute()
+    public function testEveryMinute(): void
     {
         $this->assertSame('* * * * *', $this->event->getExpression());
         $this->assertSame('* * * * *', $this->event->everyMinute()->getExpression());
     }
 
-    public function testEveryXMinutes()
+    public function testEveryXMinutes(): void
     {
         $this->assertSame('*/2 * * * *', $this->event->everyXMinutes(2)->getExpression());
         $this->expectException(InvalidArgumentException::class);
         $this->assertSame('*/2 * * * *', $this->event->everyXMinutes(-10)->getExpression());
     }
 
-    public function testDaily()
+    public function testDaily(): void
     {
         $this->assertSame('0 0 * * *', $this->event->daily()->getExpression());
     }
 
-    public function testDailyAt()
+    public function testDailyAt(): void
     {
         $this->assertSame('8 13 * * *', $this->event->dailyAt('13:08')->getExpression());
     }
 
-    public function testTwiceDailyAt()
+    public function testTwiceDailyAt(): void
     {
         $this->assertSame('0 3,15 * * *', $this->event->twiceDailyAt(3, 15)->getExpression());
         $this->assertSame('5 3,15 * * *', $this->event->twiceDailyAt(3, 15, 5)->getExpression());
     }
 
-    public function testWeekly()
+    public function testWeekly(): void
     {
         $this->assertSame('0 0 * * 0', $this->event->weekly()->getExpression());
     }
 
-    public function testWeeklyOn()
+    public function testWeeklyOn(): void
     {
         $this->assertSame('0 8 * * 1', $this->event->weeklyOn(Event::MONDAY, '8:00')->getExpression());
     }
 
-    public function testOverrideWithHourly()
+    public function testOverrideWithHourly(): void
     {
         $this->assertSame('0 * * * *', $this->event->everyXMinutes(5)->hourly()->getExpression());
         $this->assertSame('37 * * * *', $this->event->hourlyAt(37)->getExpression());
         $this->assertSame('15,30,45 * * * *', $this->event->hourlyAt([15, 30, 45])->getExpression());
     }
 
-    public function testHourly()
+    public function testHourly(): void
     {
         $this->assertSame('0 1-23/2 * * *', $this->event->everyOddHour()->getExpression());
         $this->assertSame('0 */2 * * *', $this->event->everyXHours(2)->getExpression());
@@ -80,125 +80,125 @@ public function testHourly()
         $this->assertSame('*/2 * * * *', $this->event->everyXHours(-10)->getExpression());
     }
 
-    public function testMonthly()
+    public function testMonthly(): void
     {
         $this->assertSame('0 0 1 * *', $this->event->monthly()->getExpression());
     }
 
-    public function testMonthlyOn()
+    public function testMonthlyOn(): void
     {
         $this->assertSame('0 15 4 * *', $this->event->monthlyOn(4, '15:00')->getExpression());
     }
 
-    public function testLastDayOfMonth()
+    public function testLastDayOfMonth(): void
     {
         Chronos::setTestNow('2020-10-10 10:10:10');
         $this->assertSame('0 0 31 * *', $this->event->lastDayOfMonth()->getExpression());
         Chronos::setTestNow('now');
     }
 
-    public function testTwiceMonthly()
+    public function testTwiceMonthly(): void
     {
         $this->assertSame('0 0 1,16 * *', $this->event->twiceMonthly(1, 16)->getExpression());
     }
 
-    public function testTwiceMonthlyAtTime()
+    public function testTwiceMonthlyAtTime(): void
     {
         $this->assertSame('30 1 1,16 * *', $this->event->twiceMonthly(1, 16, '1:30')->getExpression());
     }
 
-    public function testMonthlyOnWithMinutes()
+    public function testMonthlyOnWithMinutes(): void
     {
         $this->assertSame('15 15 4 * *', $this->event->monthlyOn(4, '15:15')->getExpression());
     }
 
-    public function testWeekdaysDaily()
+    public function testWeekdaysDaily(): void
     {
         $this->assertSame('0 0 * * 1-5', $this->event->weekdays()->daily()->getExpression());
     }
 
-    public function testWeekdaysHourly()
+    public function testWeekdaysHourly(): void
     {
         $this->assertSame('0 * * * 1-5', $this->event->weekdays()->hourly()->getExpression());
     }
 
-    public function testWeekdays()
+    public function testWeekdays(): void
     {
         $this->assertSame('* * * * 1-5', $this->event->weekdays()->getExpression());
     }
 
-    public function testWeekends()
+    public function testWeekends(): void
     {
         $this->assertSame('* * * * 6,0', $this->event->weekends()->getExpression());
     }
 
-    public function testSundays()
+    public function testSundays(): void
     {
         $this->assertSame('* * * * 0', $this->event->sundays()->getExpression());
     }
 
-    public function testMondays()
+    public function testMondays(): void
     {
         $this->assertSame('* * * * 1', $this->event->mondays()->getExpression());
     }
 
-    public function testTuesdays()
+    public function testTuesdays(): void
     {
         $this->assertSame('* * * * 2', $this->event->tuesdays()->getExpression());
     }
 
-    public function testWednesdays()
+    public function testWednesdays(): void
     {
         $this->assertSame('* * * * 3', $this->event->wednesdays()->getExpression());
     }
 
-    public function testThursdays()
+    public function testThursdays(): void
     {
         $this->assertSame('* * * * 4', $this->event->thursdays()->getExpression());
     }
 
-    public function testFridays()
+    public function testFridays(): void
     {
         $this->assertSame('* * * * 5', $this->event->fridays()->getExpression());
     }
 
-    public function testSaturdays()
+    public function testSaturdays(): void
     {
         $this->assertSame('* * * * 6', $this->event->saturdays()->getExpression());
     }
 
-    public function testDays()
+    public function testDays(): void
     {
         $this->assertSame('* * * * 1', $this->event->days(Event::MONDAY)->getExpression());
         $this->assertSame('* * * * 1,4', $this->event->days([Event::MONDAY, Event::THURSDAY])->getExpression());
     }
 
-    public function testQuarterly()
+    public function testQuarterly(): void
     {
         $this->assertSame('0 0 1 1-12/3 *', $this->event->quarterly()->getExpression());
     }
 
-    public function testQuarterlyOn()
+    public function testQuarterlyOn(): void
     {
         $this->assertSame('0 0 2 1-12/3 *', $this->event->quarterlyOn(2)->getExpression());
     }
 
-    public function testYearly()
+    public function testYearly(): void
     {
         $this->assertSame('0 0 1 1 *', $this->event->yearly()->getExpression());
     }
 
-    public function testYearlyOn()
+    public function testYearlyOn(): void
     {
         $this->assertSame('8 15 5 4 *', $this->event->yearlyOn(4, '5', '15:08')->getExpression());
     }
 
-    public function testYearlyOnMondaysOnly()
+    public function testYearlyOnMondaysOnly(): void
     {
         $this->assertSame('1 9 * 7 1', $this->event->mondays()->yearlyOn(7, '*', '09:01')->getExpression());
     }
 
-    public function testYearlyOnTuesdaysAndDayOfMonth20()
+    public function testYearlyOnTuesdaysAndDayOfMonth20(): void
     {
         $this->assertSame('1 9 20 7 2', $this->event->tuesdays()->yearlyOn(7, '20', '09:01')->getExpression());
     }
diff --git a/tests/TestCase/Scheduler/SchedulerTest.php b/tests/TestCase/Scheduler/SchedulerTest.php
index de3d584..ff20cea 100644
--- a/tests/TestCase/Scheduler/SchedulerTest.php
+++ b/tests/TestCase/Scheduler/SchedulerTest.php
@@ -34,7 +34,7 @@ public function testAddDueEvents(): void
     {
         $this->scheduler->execute(VersionCommand::class);
         $events = $this->scheduler->dueEvents();
-        $this->assertNotEmpty($events);
+        $this->assertFalse($events->isEmpty());
     }
 
     public function testAddMultipleDueEvents(): void