diff --git a/src/Notification/Ntfy.php b/src/Notification/Ntfy.php
index 4d53937..b45c202 100644
--- a/src/Notification/Ntfy.php
+++ b/src/Notification/Ntfy.php
@@ -14,6 +14,8 @@ use InvalidArgumentException;
  */
 class Ntfy implements NotificationInterface
 {
+    const TOPIC_MAX_LENGTH = 256;
+    const MESSAGE_MAX_LENGTH = 4096;
     private string $topic = 'default';
 
     /**
@@ -42,11 +44,11 @@ class Ntfy implements NotificationInterface
     /**
      * Set the topic of the notification message.
      *
-     * @param string $topic Topic length between 1 and 256 characters.
+     * @param string $topic Topic length between 1 and TOPIC_MAX_LENGTH characters.
      */
     public function setTopic(string $topic): void
     {
-        if (strlen($topic) < 1 || strlen($topic) >= 256) {
+        if (!strlen($topic) || strlen($topic) > self::TOPIC_MAX_LENGTH) {
             throw new InvalidArgumentException("Invalid topic length");
         }
 
@@ -66,11 +68,11 @@ class Ntfy implements NotificationInterface
      */
     public function send(string $title, string $message): void
     {
-        if (strlen($title) < 1 || strlen($title) >= 256) {
+        if (!strlen($title) || strlen($title) > self::TOPIC_MAX_LENGTH) {
             throw new InvalidArgumentException("Invalid title length");
         }
 
-        if (strlen($message) < 1 || strlen($message) >= 4096) {
+        if (!strlen($message) || strlen($message) > self::MESSAGE_MAX_LENGTH) {
             throw new InvalidArgumentException("Invalid message length");
         }
 
diff --git a/src/Template/TwigExtension.php b/src/Template/TwigExtension.php
index 44c1013..db081d1 100644
--- a/src/Template/TwigExtension.php
+++ b/src/Template/TwigExtension.php
@@ -38,7 +38,7 @@ class TwigExtension extends AbstractExtension
     public function formatBytes($bytes, $precision = 2)
     {
         $size = ['B','kB','MB','GB','TB','PB','EB','ZB','YB'];
-        $fact = (int)(floor((strlen((string)$bytes) - 1) / 3));
+        $fact = (int)floor((strlen((string)$bytes) - 1) / 3);
         return sprintf("%.{$precision}f", $bytes / pow(1024, $fact)) . $size[$fact];
     }
 }
diff --git a/tests/Notification/NtfyTest.php b/tests/Notification/NtfyTest.php
index dbb36bf..3af6c8a 100644
--- a/tests/Notification/NtfyTest.php
+++ b/tests/Notification/NtfyTest.php
@@ -30,12 +30,19 @@ final class NtfyTest extends TestCase
         $config = ['domain' => 'https://test.com', 'topic' => 'something'];
         $instance = Ntfy::factory($config);
         $this->assertInstanceOf(Ntfy::class, $instance);
+        $this->assertEquals($instance->getTopic(), "something");
     }
 
-    public function testSend(): void
+    public function testSendShort(): void
     {
         $this->client->expects($this->once())->method('send')->with($this->isInstanceOf(Message::class));
-        $this->instance->send('title', 'text');
+        $this->instance->send('t', 's');
+    }
+
+    public function testSendLong(): void
+    {
+        $this->client->expects($this->once())->method('send')->with($this->isInstanceOf(Message::class));
+        $this->instance->send(str_repeat("t", Ntfy::TOPIC_MAX_LENGTH), str_repeat("t", Ntfy::MESSAGE_MAX_LENGTH));
     }
 
     /** @return array<int, array<int, string>> */
@@ -45,8 +52,8 @@ final class NtfyTest extends TestCase
             ['', ''],
             ['', 'text'],
             ['title', ''],
-            [str_repeat("t", 256),'text'],
-            ['title',str_repeat("t", 4096)],
+            [str_repeat("t", Ntfy::TOPIC_MAX_LENGTH+1),'text'],
+            ['title',str_repeat("t", Ntfy::MESSAGE_MAX_LENGTH+1)],
         ];
     }
 
@@ -59,7 +66,11 @@ final class NtfyTest extends TestCase
 
     public function testSetTopic(): void
     {
-        $topic = "abcdefg";
+        $topic = "a";
+        $this->instance->setTopic($topic);
+        $this->assertEquals($topic, $this->instance->getTopic());
+
+        $topic = str_repeat("a", Ntfy::TOPIC_MAX_LENGTH);
         $this->instance->setTopic($topic);
         $this->assertEquals($topic, $this->instance->getTopic());
     }
@@ -69,8 +80,8 @@ final class NtfyTest extends TestCase
     {
         return [
             [''],
-            [str_repeat("t", 256)],
-            [str_repeat("t", 4096)],
+            [str_repeat("t", Ntfy::TOPIC_MAX_LENGTH+1)],
+            [str_repeat("t", Ntfy::MESSAGE_MAX_LENGTH+1)],
         ];
     }
 
diff --git a/tests/Template/TwigExtensionTest.php b/tests/Template/TwigExtensionTest.php
index 343e92e..dab15da 100644
--- a/tests/Template/TwigExtensionTest.php
+++ b/tests/Template/TwigExtensionTest.php
@@ -14,6 +14,7 @@ final class TwigExtensionTest extends \PHPUnit\Framework\TestCase
     {
         $obj = new TwigExtension();
         $filters = $obj->getFilters();
+        $this->assertNotEmpty($filters, "Filters must not be empty");
         $this->assertContainsOnlyInstancesOf(TwigFilter::class, $filters);
     }
 
@@ -31,5 +32,8 @@ final class TwigExtensionTest extends \PHPUnit\Framework\TestCase
         $this->assertEquals('1.00GB', $obj->formatBytes(1024 ** 3, 2));
         $this->assertEquals('512.00GB', $obj->formatBytes(1024 ** 4 / 2, 2));
         $this->assertEquals('1.00TB', $obj->formatBytes(1024 ** 4, 2));
+
+        $this->assertEquals('1.00B', $obj->formatBytes(1));
+        $this->assertEquals('1.00TB', $obj->formatBytes(1024 ** 4));
     }
 }
diff --git a/tests/Template/TwigTest.php b/tests/Template/TwigTest.php
index 2dd456f..a2ce7be 100644
--- a/tests/Template/TwigTest.php
+++ b/tests/Template/TwigTest.php
@@ -17,4 +17,12 @@ final class TwigTest extends \PHPUnit\Framework\TestCase
         $output = $template->render(['var' => 'middle']);
         $this->assertEquals('start middle end', $output);
     }
+
+    public function testExtensionsLoaded(): void
+    {
+        $obj = new Twig(['template' => 'start {{ var | formatBytes}} end']);
+        $template = $obj->load('template');
+        $output = $template->render(['var' => 1]);
+        $this->assertEquals('start 1.00B end', $output);
+    }
 }