diff --git a/.gitattributes b/.gitattributes
index b157bef..a9c1856 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,7 +1,7 @@
 # Ignore all test and documentation with “export-ignore”.
 /.gitattributes export-ignore
 /.gitignore export-ignore
-/.php_cs export-ignore
+/.php-cs-fixer.php export-ignore
 /.github export-ignore
 /README.md export-ignore
 /phpunit.xml export-ignore
diff --git a/.gitignore b/.gitignore
index 3bc18f6..3bca77e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,5 @@
 /vendor/
-/.php-cs-fixer.cache
-/.phpunit.result.cache
+/.*.cache
 /tests-report-html/
 /composer.lock
-/coverage.xml
\ No newline at end of file
+/coverage.xml
diff --git a/composer.json b/composer.json
index d0883fb..fdb36f9 100644
--- a/composer.json
+++ b/composer.json
@@ -26,6 +26,7 @@
   "require-dev": {
     "friendsofphp/php-cs-fixer": "^3.0",
     "phpstan/phpstan": "^1.0",
+    "phpstan/phpstan-phpunit": "^1.0",
     "phpstan/phpstan-strict-rules": "^1.0",
     "phpstan/phpstan-webmozart-assert": "^1.0",
     "phpunit/phpunit": "^7.0 || ^8.0 || ^9.0"
diff --git a/phpstan.neon b/phpstan.neon
index fe322e2..74fd7ea 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,3 +1,5 @@
 includes:
+    - vendor/phpstan/phpstan-phpunit/extension.neon
+    - vendor/phpstan/phpstan-phpunit/rules.neon
     - vendor/phpstan/phpstan-strict-rules/rules.neon
     - vendor/phpstan/phpstan-webmozart-assert/extension.neon
\ No newline at end of file
diff --git a/phpunit.xml b/phpunit.xml
index 96ca32c..01dcc3a 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -3,15 +3,15 @@
          xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
          bootstrap="vendor/autoload.php"
          colors="true">
+    <coverage>
+        <include>
+            <directory suffix=".php">src</directory>
+            <directory suffix=".php">tests</directory>
+        </include>
+    </coverage>
     <testsuites>
         <testsuite name="default">
             <directory>tests</directory>
         </testsuite>
     </testsuites>
-    <filter>
-        <whitelist>
-            <directory suffix=".php">src</directory>
-            <directory suffix=".php">tests</directory>
-        </whitelist>
-    </filter>
 </phpunit>
\ No newline at end of file
diff --git a/src/Feed.php b/src/Feed.php
index 2d0d31d..cc17d35 100644
--- a/src/Feed.php
+++ b/src/Feed.php
@@ -3,6 +3,7 @@
 namespace AtomGenerator;
 
 use DOMDocument;
+use Exception;
 use LibXMLError;
 use SimpleXMLElement;
 use Webmozart\Assert\Assert;
@@ -37,7 +38,7 @@ class Feed extends AbstractElement
     protected $generatorUri;
 
     /**
-     * @var mixed[][]
+     * @var array[]
      * @phpstan-var array<array{ns: string, uri: string, name: string, value: string, attributes: string[]}>
      */
     protected $customElements = [];
@@ -169,6 +170,9 @@ public function addChildrenTo(SimpleXMLElement $parent): void
         }
     }
 
+    /**
+     * @throws Exception
+     */
     public function getSimpleXML(): SimpleXMLElement
     {
         $attributes = [];
@@ -191,6 +195,9 @@ public function getSimpleXML(): SimpleXMLElement
         return $xml;
     }
 
+    /**
+     * @throws Exception
+     */
     public function getDocument(): DOMDocument
     {
         $node = dom_import_simplexml($this->getSimpleXML());
@@ -202,6 +209,8 @@ public function getDocument(): DOMDocument
     }
 
     /**
+     * @throws Exception
+     *
      * @return false|string
      */
     public function saveXML()
diff --git a/tests/FeedTest.php b/tests/FeedTest.php
index 09c4ca8..fc7586a 100644
--- a/tests/FeedTest.php
+++ b/tests/FeedTest.php
@@ -5,6 +5,7 @@
 use AtomGenerator\Entry;
 use AtomGenerator\Feed;
 use DateTime;
+use Exception;
 use InvalidArgumentException;
 use LibXMLError;
 use PHPUnit\Framework\TestCase;
@@ -22,6 +23,9 @@ final class FeedTest extends TestCase
     /** @var bool reset file contents */
     protected static $reset = false;
 
+    /**
+     * @throws Exception
+     */
     public function testFeedCreation1(): void
     {
         $feed = new Feed();
@@ -72,6 +76,9 @@ public function testFeedCreation1(): void
         self::assertXmlStringEqualsXmlFile(self::TEST_FEED_XML_PATH_1, $xml);
     }
 
+    /**
+     * @throws Exception
+     */
     public function testFeedCreation2(): void
     {
         $feed = new Feed();
@@ -104,6 +111,9 @@ public function testFeedCreation2(): void
         self::assertXmlStringEqualsXmlFile(self::TEST_FEED_XML_PATH_2, $xml);
     }
 
+    /**
+     * @throws Exception
+     */
     public function testFeedCreation3(): void
     {
         $feed = new Feed();
@@ -132,6 +142,9 @@ public function testFeedCreation3(): void
         self::assertXmlStringEqualsXmlFile(self::TEST_FEED_XML_PATH_3, $xml);
     }
 
+    /**
+     * @throws Exception
+     */
     public function testFeedCreation4(): void
     {
         $sourceFeed = new Feed();
@@ -198,6 +211,8 @@ public function testFeedCreationException3(): void
 
     /**
      * @codeCoverageIgnore
+     *
+     * @throws Exception
      */
     public function testFeedCreationException4(): void
     {