diff --git a/composer.json b/composer.json
index ce1fd809..519ca8c7 100644
--- a/composer.json
+++ b/composer.json
@@ -45,7 +45,8 @@
     },
     "config": {
         "allow-plugins": {
-            "composer/package-versions-deprecated": true
+            "composer/package-versions-deprecated": true,
+            "dealerdirect/phpcodesniffer-composer-installer": true
         }
     }
 }
diff --git a/src/AbstractElement.php b/src/AbstractElement.php
index a4b39b69..4bbce476 100644
--- a/src/AbstractElement.php
+++ b/src/AbstractElement.php
@@ -6,10 +6,10 @@
 
 use DOMElement;
 use RuntimeException;
+use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\MissingAttributeException;
 use SimpleSAML\XML\Exception\SchemaViolationException;
 use SimpleSAML\XML\SerializableElementTrait;
-use SimpleSAML\Assert\Assert;
 
 use function array_slice;
 use function defined;
diff --git a/src/ArrayizableElementInterface.php b/src/ArrayizableElementInterface.php
index bb11436c..27a995a3 100644
--- a/src/ArrayizableElementInterface.php
+++ b/src/ArrayizableElementInterface.php
@@ -4,8 +4,6 @@
 
 namespace SimpleSAML\XML;
 
-use DOMElement;
-
 /**
  * interface class to be implemented by all the classes that represent an arrayizable XML element
  *
diff --git a/src/Base64ElementTrait.php b/src/Base64ElementTrait.php
index e72e524c..0a604a0e 100644
--- a/src/Base64ElementTrait.php
+++ b/src/Base64ElementTrait.php
@@ -6,10 +6,8 @@
 
 use DOMElement;
 use SimpleSAML\Assert\Assert;
-use SimpleSAML\XML\Constants;
-use SimpleSAML\XML\StringElementTrait;
-use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\SchemaViolationException;
+use SimpleSAML\XML\StringElementTrait;
 
 use function str_replace;
 
diff --git a/src/Chunk.php b/src/Chunk.php
index 4215aa70..97926ff9 100644
--- a/src/Chunk.php
+++ b/src/Chunk.php
@@ -9,9 +9,7 @@
 use SimpleSAML\XML\Exception\MissingAttributeException;
 use SimpleSAML\XML\Exception\SchemaViolationException;
 use SimpleSAML\XML\SerializableElementTrait;
-use SimpleSAML\XML\Utils;
 
-use function func_num_args;
 use function in_array;
 use function intval;
 
diff --git a/src/DOMDocumentFactory.php b/src/DOMDocumentFactory.php
index 31a2f79c..25998ac5 100644
--- a/src/DOMDocumentFactory.php
+++ b/src/DOMDocumentFactory.php
@@ -5,7 +5,6 @@
 namespace SimpleSAML\XML;
 
 use DOMDocument;
-use InvalidArgumentException;
 use RuntimeException;
 use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\IOException;
@@ -13,8 +12,6 @@
 
 use function defined;
 use function file_get_contents;
-use function is_file;
-use function is_readable;
 use function libxml_clear_errors;
 use function libxml_get_last_error;
 use function libxml_use_internal_errors;
diff --git a/src/ExtendableElementTrait.php b/src/ExtendableElementTrait.php
index ead62b8b..6b91aa96 100644
--- a/src/ExtendableElementTrait.php
+++ b/src/ExtendableElementTrait.php
@@ -4,7 +4,6 @@
 
 namespace SimpleSAML\XML;
 
-use DOMElement;
 use RuntimeException;
 use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Chunk;
diff --git a/src/QNameElementTrait.php b/src/QNameElementTrait.php
index d24eb843..5cf5095d 100644
--- a/src/QNameElementTrait.php
+++ b/src/QNameElementTrait.php
@@ -6,7 +6,6 @@
 
 use DOMElement;
 use SimpleSAML\Assert\Assert;
-use SimpleSAML\XML\Constants;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\SchemaViolationException;
 use SimpleSAML\XML\StringElementTrait;
diff --git a/src/SerializableElementTrait.php b/src/SerializableElementTrait.php
index b58d9b9d..a97e1f42 100644
--- a/src/SerializableElementTrait.php
+++ b/src/SerializableElementTrait.php
@@ -5,8 +5,6 @@
 namespace SimpleSAML\XML;
 
 use DOMElement;
-use RuntimeException;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\DOMDocumentFactory;
 
 use function array_pop;
diff --git a/src/StringElementTrait.php b/src/StringElementTrait.php
index 08ff9b2e..835ca906 100644
--- a/src/StringElementTrait.php
+++ b/src/StringElementTrait.php
@@ -6,7 +6,6 @@
 
 use DOMElement;
 use SimpleSAML\Assert\Assert;
-use SimpleSAML\XML\Constants;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 
 /**
diff --git a/src/TestUtils/ArrayizableElementTestTrait.php b/src/TestUtils/ArrayizableElementTestTrait.php
index 8a3eecfe..2ff77584 100644
--- a/src/TestUtils/ArrayizableElementTestTrait.php
+++ b/src/TestUtils/ArrayizableElementTestTrait.php
@@ -4,8 +4,6 @@
 
 namespace SimpleSAML\XML\TestUtils;
 
-use DOMDocument;
-
 use function class_exists;
 
 /**
diff --git a/src/Utils/XPath.php b/src/Utils/XPath.php
index c7203db8..4449ffa0 100644
--- a/src/Utils/XPath.php
+++ b/src/Utils/XPath.php
@@ -5,10 +5,8 @@
 namespace SimpleSAML\XML\Utils;
 
 use DOMDocument;
-use DOMElement;
 use DOMNode;
 use DOMXPath;
-use InvalidArgumentException;
 use SimpleSAML\Assert\Assert;
 
 /**
diff --git a/tests/Utils/ExtendableAttributesElement.php b/tests/Utils/ExtendableAttributesElement.php
index faebdbda..17bb59d9 100644
--- a/tests/Utils/ExtendableAttributesElement.php
+++ b/tests/Utils/ExtendableAttributesElement.php
@@ -6,11 +6,10 @@
 
 use DOMElement;
 use SimpleSAML\Assert\Assert;
-use SimpleSAML\Assert\AssertionFailedException;
 use SimpleSAML\XML\AbstractElement;
-use SimpleSAML\XML\XsNamespace as NS;
-use SimpleSAML\XML\ExtendableAttributesTrait;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
+use SimpleSAML\XML\ExtendableAttributesTrait;
+use SimpleSAML\XML\XsNamespace as NS;
 
 /**
  * Empty shell class for testing ExtendableAttributesTrait.
diff --git a/tests/Utils/ExtendableElement.php b/tests/Utils/ExtendableElement.php
index 9ba5166d..9469aa2b 100644
--- a/tests/Utils/ExtendableElement.php
+++ b/tests/Utils/ExtendableElement.php
@@ -5,13 +5,11 @@
 namespace SimpleSAML\Test\XML;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\AbstractElement;
 use SimpleSAML\XML\Chunk;
-use SimpleSAML\XML\XsNamespace as NS;
 use SimpleSAML\XML\ExtendableElementTrait;
-use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\SerializableElementTrait;
+use SimpleSAML\XML\XsNamespace as NS;
 
 /**
  * Empty shell class for testing ExtendableElementTrait.
diff --git a/tests/Utils/QNameElement.php b/tests/Utils/QNameElement.php
index 502e0af8..6739765d 100644
--- a/tests/Utils/QNameElement.php
+++ b/tests/Utils/QNameElement.php
@@ -4,8 +4,8 @@
 
 namespace SimpleSAML\Test\XML;
 
-use SimpleSAML\XML\QNameElementTrait;
 use SimpleSAML\XML\AbstractElement;
+use SimpleSAML\XML\QNameElementTrait;
 
 /**
  * Empty shell class for testing QNameElement.
diff --git a/tests/Utils/StringElement.php b/tests/Utils/StringElement.php
index d3dc8990..93cef670 100644
--- a/tests/Utils/StringElement.php
+++ b/tests/Utils/StringElement.php
@@ -5,7 +5,6 @@
 namespace SimpleSAML\Test\XML;
 
 use SimpleSAML\XML\AbstractElement;
-use SimpleSAML\XML\SerializableElementTrait;
 use SimpleSAML\XML\StringElementTrait;
 
 /**
diff --git a/tests/XML/AbstractElementTest.php b/tests/XML/AbstractElementTest.php
index cf6a3300..2412ddfd 100644
--- a/tests/XML/AbstractElementTest.php
+++ b/tests/XML/AbstractElementTest.php
@@ -6,7 +6,6 @@
 
 use PHPUnit\Framework\TestCase;
 use SimpleSAML\Test\XML\Element;
-use SimpleSAML\XML\AbstractElement;
 use SimpleSAML\XML\DOMDocumentFactory;
 use SimpleSAML\XML\Exception\MissingAttributeException;
 use SimpleSAML\XML\TestUtils\SerializableElementTestTrait;
diff --git a/tests/XML/AttributeTest.php b/tests/XML/AttributeTest.php
index 4798edae..92dce9ef 100644
--- a/tests/XML/AttributeTest.php
+++ b/tests/XML/AttributeTest.php
@@ -6,13 +6,10 @@
 
 use DOMDocument;
 use PHPUnit\Framework\TestCase;
-use SimpleSAML\XML\Constants as C;
-use SimpleSAML\XML\DOMDocumentFactory;
 use SimpleSAML\XML\Attribute;
+use SimpleSAML\XML\DOMDocumentFactory;
 use SimpleSAML\XML\TestUtils\ArrayizableElementTestTrait;
 
-use function dirname;
-
 /**
  * Class \SimpleSAML\XML\AttributeTest
  *
diff --git a/tests/XML/Base64ElementTraitTest.php b/tests/XML/Base64ElementTraitTest.php
index 8b5e140c..29d33895 100644
--- a/tests/XML/Base64ElementTraitTest.php
+++ b/tests/XML/Base64ElementTraitTest.php
@@ -5,12 +5,8 @@
 namespace SimpleSAML\Test\XML;
 
 use PHPUnit\Framework\TestCase;
-use SimpleSAML\Assert\Assert;
-use SimpleSAML\Test\XML\Base64EStringlement;
 use SimpleSAML\Test\XML\XMLDumper;
-use SimpleSAML\XML\AbstractElement;
 use SimpleSAML\XML\DOMDocumentFactory;
-use SimpleSAML\XML\Base64ElementTrait;
 use SimpleSAML\XML\TestUtils\SerializableElementTestTrait;
 
 use function dirname;
diff --git a/tests/XML/DOMDocumentFactoryTest.php b/tests/XML/DOMDocumentFactoryTest.php
index ea640dfa..c15d1738 100644
--- a/tests/XML/DOMDocumentFactoryTest.php
+++ b/tests/XML/DOMDocumentFactoryTest.php
@@ -4,9 +4,8 @@
 
 namespace SimpleSAML\Test\XML;
 
-use InvalidArgumentException;
-use RuntimeException;
 use PHPUnit\Framework\TestCase;
+use RuntimeException;
 use SimpleSAML\Assert\AssertionFailedException;
 use SimpleSAML\XML\DOMDocumentFactory;
 use SimpleSAML\XML\Exception\UnparseableXMLException;
diff --git a/tests/XML/Exception/IOExceptionTest.php b/tests/XML/Exception/IOExceptionTest.php
index 94eadc0f..6aec9750 100644
--- a/tests/XML/Exception/IOExceptionTest.php
+++ b/tests/XML/Exception/IOExceptionTest.php
@@ -4,7 +4,6 @@
 
 namespace SimpleSAML\Test\XML;
 
-use LibXMLError;
 use PHPUnit\Framework\TestCase;
 use SimpleSAML\XML\Exception\IOException;
 
diff --git a/tests/XML/Exception/UnparseableXMLExceptionTest.php b/tests/XML/Exception/UnparseableXMLExceptionTest.php
index f93a7e6c..557d004d 100644
--- a/tests/XML/Exception/UnparseableXMLExceptionTest.php
+++ b/tests/XML/Exception/UnparseableXMLExceptionTest.php
@@ -5,7 +5,6 @@
 namespace SimpleSAML\Test\XML;
 
 use LibXMLError;
-use LIBXML_ERR_ERROR;
 use PHPUnit\Framework\TestCase;
 use SimpleSAML\XML\Exception\UnparseableXMLException;
 
diff --git a/tests/XML/ExtendableAttributesTraitTest.php b/tests/XML/ExtendableAttributesTraitTest.php
index a5cb94f8..307c72d8 100644
--- a/tests/XML/ExtendableAttributesTraitTest.php
+++ b/tests/XML/ExtendableAttributesTraitTest.php
@@ -5,16 +5,11 @@
 namespace SimpleSAML\Test\XML;
 
 use PHPUnit\Framework\TestCase;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\Assert\AssertionFailedException;
 use SimpleSAML\Test\XML\ExtendableAttributesElement;
-use SimpleSAML\Test\XML\ExtendableAttributesTestTrait;
 use SimpleSAML\XML\Attribute;
-use SimpleSAML\XML\DOMDocumentFactory;
 use SimpleSAML\XML\XsNamespace as NS;
 
-use function dirname;
-
 /**
  * Class \SimpleSAML\XML\ExtendableAttributesTraitTest
  *
diff --git a/tests/XML/ExtendableElementTest.php b/tests/XML/ExtendableElementTest.php
index 8e5238c9..d0ae1fcd 100644
--- a/tests/XML/ExtendableElementTest.php
+++ b/tests/XML/ExtendableElementTest.php
@@ -5,14 +5,13 @@
 namespace SimpleSAML\Test\XML;
 
 use PHPUnit\Framework\TestCase;
-use SimpleSAML\Test\XML\ExtendableElementElement;
 use SimpleSAML\XML\Chunk;
 use SimpleSAML\XML\DOMDocumentFactory;
 use SimpleSAML\XML\TestUtils\SchemaValidationTestTrait;
 use SimpleSAML\XML\TestUtils\SerializableElementTestTrait;
-use SimpleSAML\XML\Attribute;
 
 use function dirname;
+use function strval;
 
 /**
  * Class \SimpleSAML\XML\ExtendableElementTest
diff --git a/tests/XML/ExtendableElementTraitTest.php b/tests/XML/ExtendableElementTraitTest.php
index c2efe832..744da6f8 100644
--- a/tests/XML/ExtendableElementTraitTest.php
+++ b/tests/XML/ExtendableElementTraitTest.php
@@ -12,8 +12,6 @@
 use SimpleSAML\XML\ElementInterface;
 use SimpleSAML\XML\XsNamespace as NS;
 
-use function dirname;
-
 /**
  * Class \SimpleSAML\XML\ExtendableElementTraitTest
  *
diff --git a/tests/XML/LocalizedStringElementTraitTest.php b/tests/XML/LocalizedStringElementTraitTest.php
index 968b8e5c..c4198ade 100644
--- a/tests/XML/LocalizedStringElementTraitTest.php
+++ b/tests/XML/LocalizedStringElementTraitTest.php
@@ -6,9 +6,7 @@
 
 use PHPUnit\Framework\TestCase;
 use SimpleSAML\Test\XML\LocalizedStringElement;
-use SimpleSAML\XML\AbstractElement;
 use SimpleSAML\XML\DOMDocumentFactory;
-use SimpleSAML\XML\StringElementTrait;
 use SimpleSAML\XML\TestUtils\SerializableElementTestTrait;
 
 use function dirname;
diff --git a/tests/XML/QNameElementTraitTest.php b/tests/XML/QNameElementTraitTest.php
index 35f2fa2c..100a64b3 100644
--- a/tests/XML/QNameElementTraitTest.php
+++ b/tests/XML/QNameElementTraitTest.php
@@ -5,9 +5,6 @@
 namespace SimpleSAML\Test\XML;
 
 use PHPUnit\Framework\TestCase;
-use SimpleSAML\Assert\Assert;
-use SimpleSAML\Test\XML\QNamelement;
-use SimpleSAML\XML\AbstractElement;
 use SimpleSAML\XML\DOMDocumentFactory;
 use SimpleSAML\XML\Exception\SchemaViolationException;
 use SimpleSAML\XML\TestUtils\SerializableElementTestTrait;
diff --git a/tests/XML/StringElementTraitTest.php b/tests/XML/StringElementTraitTest.php
index 14893ab3..5b2750cb 100644
--- a/tests/XML/StringElementTraitTest.php
+++ b/tests/XML/StringElementTraitTest.php
@@ -6,9 +6,7 @@
 
 use PHPUnit\Framework\TestCase;
 use SimpleSAML\Test\XML\StringElement;
-use SimpleSAML\XML\AbstractElement;
 use SimpleSAML\XML\DOMDocumentFactory;
-use SimpleSAML\XML\StringElementTrait;
 use SimpleSAML\XML\TestUtils\SerializableElementTestTrait;
 
 use function dirname;