diff --git a/composer.json b/composer.json
index c0b4715..8a62d3a 100644
--- a/composer.json
+++ b/composer.json
@@ -1,7 +1,12 @@
 {
-    "name":"yosymfony/resource-watcher",
+    "name": "yosymfony/resource-watcher",
     "description": "A simple resource watcher using Symfony Finder",
-    "keywords": ["resources","watcher","finder","symfony"],
+    "keywords": [
+        "resources",
+        "watcher",
+        "finder",
+        "symfony"
+    ],
     "license": "MIT",
     "homepage": "http://yosymfony.com",
     "authors": [
@@ -11,12 +16,12 @@
         }
     ],
     "require": {
-        "php": ">=5.6",
-        "symfony/finder": "^2.7|^3.0|^4.0|^5.0"
+        "php": ">=7.4",
+        "symfony/finder": "^2.7|^3.0|^4.0|^5.0|^6.0"
     },
     "require-dev": {
         "symfony/filesystem": "^2.7|^3.0|^4.0|^5.0",
-        "phpunit/phpunit": "^5.7"
+        "phpunit/phpunit": "^9.0"
     },
     "autoload": {
         "psr-4": {
@@ -31,4 +36,4 @@
     "scripts": {
         "test": "vendor/bin/phpunit"
     }
-}
+}
\ No newline at end of file
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index c65e8db..08a506d 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,29 +1,27 @@
 <?xml version="1.0" encoding="UTF-8"?>
-
-<phpunit backupGlobals="false"
-         backupStaticAttributes="false"
-         colors="true"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="true"
-         convertWarningsToExceptions="true"
-         processIsolation="false"
-         stopOnFailure="false"
-         syntaxCheck="false"
-         bootstrap="vendor/autoload.php"
->
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    backupGlobals="false"
+    backupStaticAttributes="false"
+    colors="true"
+    convertErrorsToExceptions="true"
+    convertNoticesToExceptions="true"
+    convertWarningsToExceptions="true"
+    processIsolation="false"
+    stopOnFailure="false"
+    bootstrap="vendor/autoload.php"
+    xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd">
+    <coverage>
+        <include>
+            <directory>./</directory>
+        </include>
+        <exclude>
+            <directory>./vendor</directory>
+            <directory>./tests</directory>
+        </exclude>
+    </coverage>
     <testsuites>
         <testsuite name="Resource Watcher Test Suite">
             <directory>./tests</directory>
         </testsuite>
     </testsuites>
-
-    <filter>
-        <whitelist>
-            <directory>./</directory>
-            <exclude>
-                <directory>./vendor</directory>
-                <directory>./tests</directory>
-            </exclude>
-        </whitelist>
-    </filter>
 </phpunit>
\ No newline at end of file
diff --git a/src/ResourceCachePhpFile.php b/src/ResourceCachePhpFile.php
index 66f8594..4f5cf64 100644
--- a/src/ResourceCachePhpFile.php
+++ b/src/ResourceCachePhpFile.php
@@ -11,6 +11,8 @@
 
 namespace Yosymfony\ResourceWatcher;
 
+use InvalidArgumentException;
+
 /**
  * Resource cache implementation using a PHP file with an array.
  *
@@ -73,7 +75,7 @@ public function save()
     private function warmUpCacheFromFile($filename)
     {
         if (preg_match('#\.php$#', $filename) == false) {
-            throw new \InvalidArgumentException('The cache filename must ends with the extension ".php".');
+            throw new InvalidArgumentException('The cache filename must ends with the extension ".php".');
         }
 
         if (file_exists($filename) == false) {
@@ -84,8 +86,8 @@ private function warmUpCacheFromFile($filename)
 
         $fileContent = include($filename);
 
-        if (is_array($fileContent) == false) {
-            throw new \InvalidArgumentException('Cache file invalid format.');
+        if (is_array($fileContent) === false) {
+            throw new InvalidArgumentException('Cache file invalid format.');
         }
 
         foreach ($fileContent as $filename => $hash) {
diff --git a/tests/ResourceCacheMemoryTest.php b/tests/ResourceCacheMemoryTest.php
index a46cf68..7da1520 100644
--- a/tests/ResourceCacheMemoryTest.php
+++ b/tests/ResourceCacheMemoryTest.php
@@ -18,7 +18,7 @@ class ResourceCacheMemoryTest extends TestCase
 {
     private $cache;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->cache = new ResourceCacheMemory();
     }
diff --git a/tests/ResourceCachePhpFileTest.php b/tests/ResourceCachePhpFileTest.php
index bfdb1f5..f7c498b 100644
--- a/tests/ResourceCachePhpFileTest.php
+++ b/tests/ResourceCachePhpFileTest.php
@@ -11,6 +11,7 @@
 
 namespace Yosymfony\ResourceWatcher\Tests;
 
+use InvalidArgumentException;
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Filesystem\Filesystem;
 use Yosymfony\ResourceWatcher\ResourceCachePhpFile;
@@ -21,7 +22,7 @@ class ResourceCachePhpFileTest extends TestCase
     private $fs;
     private $tmpDir;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->tmpDir = sys_get_temp_dir() . '/resource-watchers-tests';
         $this->cacheFile = $this->tmpDir . '/cache-file-test.php';
@@ -29,7 +30,7 @@ public function setUp()
         $this->fs->mkdir($this->tmpDir);
     }
 
-    public function tearDown()
+    public function tearDown(): void
     {
         $this->fs->remove($this->tmpDir);
     }
@@ -78,6 +79,8 @@ public function testConstructWithAInvalidCacheFileMustThrownAnException()
     {
         $this->fs->dumpFile($this->cacheFile, '');
 
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Cache file invalid format.');
         $rc = new ResourceCachePhpFile($this->cacheFile);
     }
 
@@ -87,6 +90,9 @@ public function testConstructWithAInvalidCacheFileMustThrownAnException()
      */
     public function testConstructWithANoPhpFileExtensionMustThrownAnException()
     {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('The cache filename must ends with the extension ".php".');
+
         $rc = new ResourceCachePhpFile($this->tmpDir . '/cache-file-test.txt');
     }
 }
diff --git a/tests/ResourceWatcherResultTest.php b/tests/ResourceWatcherResultTest.php
index e884487..069735a 100644
--- a/tests/ResourceWatcherResultTest.php
+++ b/tests/ResourceWatcherResultTest.php
@@ -21,7 +21,7 @@ class ResourceWatcherResultTests extends TestCase
     private $updatedFiles;
     private $resourceWatcherResult;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->newFiles = ['/my-path/newfile.txt'];
         $this->deletedFiles = ['/my-path/deletedfile.txt'];
diff --git a/tests/ResourceWatcherTest.php b/tests/ResourceWatcherTest.php
index 9260a34..57ed02e 100644
--- a/tests/ResourceWatcherTest.php
+++ b/tests/ResourceWatcherTest.php
@@ -23,7 +23,7 @@ class ResourceWatcherTest extends TestCase
     protected $tmpDir;
     protected $fs;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->tmpDir = sys_get_temp_dir() . '/resourceWatcher-tests';
         $this->fs = new Filesystem();
@@ -31,7 +31,7 @@ public function setUp()
         $this->fs->mkdir($this->tmpDir);
     }
 
-    public function tearDown()
+    public function tearDown(): void
     {
         $this->fs->remove($this->tmpDir);
     }