diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 01ee669..784edfb 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -6,9 +6,9 @@ jobs:
     strategy:
       matrix:
         php-version:
-          - '5.6'
-          - '7.0'
-          - '7.4'
+          - '8.1'
+          - '8.2'
+          - '8.3'
     name: PHP ${{ matrix.php-version }} sample
     steps:
       - uses: actions/checkout@v3
diff --git a/.gitignore b/.gitignore
index 460a86c..7cda81c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,6 +7,8 @@ Icon
 .Spotlight-V100
 .Trashes
 *.sublime-*
+.phpunit.result.cache
+.env
 vendor
 composer.lock
 bin
\ No newline at end of file
diff --git a/composer.json b/composer.json
index 9da6e1f..740eba5 100644
--- a/composer.json
+++ b/composer.json
@@ -12,12 +12,12 @@
         }
     ],
     "require": {
-        "php": ">=5.4.0",
+        "php": ">=8.0",
         "ext-curl": "*",
         "ext-json": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "~4.0"
+        "phpunit/phpunit": "~10.0"
     },
     "config": {
         "bin-dir": "bin"
diff --git a/docker-compose.yml b/docker-compose.yml
new file mode 100644
index 0000000..192fe03
--- /dev/null
+++ b/docker-compose.yml
@@ -0,0 +1,26 @@
+version: '3.8'
+
+services:
+  php81:
+    image: php:8.1-cli
+    env_file: .env
+    volumes:
+      - .:/app
+    working_dir: /app
+    command: bin/phpunit
+
+  php82:
+    image: php:8.2-cli
+    env_file: .env
+    volumes:
+      - .:/app
+    working_dir: /app
+    command: bin/phpunit
+
+  php83:
+    image: php:8.3-cli
+    env_file: .env
+    volumes:
+      - .:/app
+    working_dir: /app
+    command: bin/phpunit
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 1010532..0e55e53 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,13 +1,21 @@
-<phpunit bootstrap="vendor/autoload.php" colors="true">
-    <testsuites>
-        <testsuite name="ConvertApi Test Suite">
-            <directory suffix="Test.php">./tests/ConvertApi/</directory>
-        </testsuite>
-    </testsuites>
-
-    <filter>
-        <whitelist>
-            <directory suffix=".php">./lib/ConvertApi/</directory>
-        </whitelist>
-    </filter>
+<?xml version="1.0"?>
+<phpunit 
+  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd"
+  bootstrap="vendor/autoload.php"
+  displayDetailsOnTestsThatTriggerDeprecations="true"
+  displayDetailsOnTestsThatTriggerErrors="true"
+  displayDetailsOnTestsThatTriggerNotices="true"
+  displayDetailsOnTestsThatTriggerWarnings="true"
+>
+  <testsuites>
+    <testsuite name="ConvertApi Test Suite">
+      <directory suffix="Test.php">./tests/ConvertApi/</directory>
+    </testsuite>
+  </testsuites>
+  <source restrictDeprecations="true">
+    <include>
+      <directory suffix=".php">./lib/ConvertApi/</directory>
+    </include>
+  </source>
 </phpunit>
diff --git a/tests/ConvertApi/ConvertApiTest.php b/tests/ConvertApi/ConvertApiTest.php
index 3cb76f5..0525798 100644
--- a/tests/ConvertApi/ConvertApiTest.php
+++ b/tests/ConvertApi/ConvertApiTest.php
@@ -4,11 +4,11 @@
 
 use \ConvertApi\ConvertApi;
 
-class ConvertApiTest extends \PHPUnit_Framework_TestCase
+class ConvertApiTest extends \PHPUnit\Framework\TestCase
 {
     protected $origApiSecret;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         // Save original values so that we can restore them after running tests
         $this->origApiSecret = ConvertApi::getApiSecret();
@@ -18,7 +18,7 @@ protected function setUp()
         ConvertApi::setApiSecret(getenv('CONVERT_API_SECRET'));
     }
 
-    protected function tearDown()
+    protected function tearDown(): void
     {
         // Restore original values
         ConvertApi::setApiSecret($this->origApiSecret);
@@ -44,7 +44,7 @@ public function testGetUser()
     {
         $user_info = ConvertApi::getUser();
 
-        $this->assertInternalType('array', $user_info);
+        $this->assertIsArray($user_info);
         $this->assertArrayHasKey('SecondsLeft', $user_info);
     }
 
@@ -56,7 +56,7 @@ public function testConvertWithFileUrl()
 
         $this->assertInstanceOf('\ConvertApi\Result', $result);
 
-        $this->assertInternalType('int', $result->getConversionCost());
+        $this->assertIsInt($result->getConversionCost());
 
         $files = $result->saveFiles(sys_get_temp_dir());
 
@@ -65,7 +65,7 @@ public function testConvertWithFileUrl()
         foreach ($files as $file)
             unlink($file);
 
-        $this->assertInternalType('string', $result->getFile()->getContents());
+        $this->assertIsString($result->getFile()->getContents());
     }
 
     public function testConvertWithFilePath()
@@ -123,7 +123,7 @@ public function testConvertWithSpecifiedSourceFormatAndTimeout()
 
         $result = ConvertApi::convert('pdf', $params, 'web', 100);
 
-        $this->assertInternalType('int', $result->getFile()->getFileSize());
+        $this->assertIsInt($result->getFile()->getFileSize());
     }
 
     public function testConvertWithMultipleFiles()
@@ -143,7 +143,7 @@ public function testConvertWithUrl()
 
         $result = ConvertApi::convert('pdf', $params, 'web');
 
-        $this->assertInternalType('int', $result->getFile()->getFileSize());
+        $this->assertIsInt($result->getFile()->getFileSize());
     }
 
     public function testChainedConversion()
@@ -180,7 +180,7 @@ public function testApiError()
 
             $this->fail('Expected exception has not been raised.');
         } catch (\ConvertApi\Error\Api $e) {
-            $this->assertContains('Parameter validation error.', $e->getMessage());
+            $this->assertStringContainsString('Parameter validation error.', $e->getMessage());
             $this->assertEquals(4000, $e->getCode());
         }
     }
@@ -196,7 +196,7 @@ public function testClientError()
 
             $this->fail('Expected exception has not been raised.');
         } catch (\ConvertApi\Error\Client $e) {
-            $this->assertContains('timed out', $e->getMessage());
+            $this->assertStringContainsString('timed out', $e->getMessage());
             $this->assertEquals(28, $e->getCode());
         }
     }