diff --git a/.gitignore b/.gitignore
index 87904ecb..f2b1db6b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,5 +4,6 @@
 /docs/html/
 /laminas-mkdoc-theme.tgz
 /laminas-mkdoc-theme/
+/.phpunit.result.cache
 /phpunit.xml
 /vendor/
diff --git a/.travis.yml b/.travis.yml
index d63ede4b..677679fc 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,36 +12,24 @@ env:
 matrix:
   fast_finish: true
   include:
-    - php: 5.6
-      env:
-        - DEPS=lowest
-    - php: 5.6
-      env:
-        - DEPS=latest
-    - php: 7
-      env:
-        - DEPS=lowest
-    - php: 7
-      env:
-        - DEPS=latest
-    - php: 7.1
+    - php: 7.3
       env:
         - DEPS=lowest
-    - php: 7.1
+    - php: 7.3
       env:
         - DEPS=latest
         - CS_CHECK=true
         - TEST_COVERAGE=true
-    - php: 7.2
+    - php: 7.4
       env:
         - DEPS=lowest
-    - php: 7.2
+    - php: 7.4
       env:
         - DEPS=latest
-    - php: 7.3
+    - php: 8.0
       env:
         - DEPS=lowest
-    - php: 7.3
+    - php: 8.0
       env:
         - DEPS=latest
 
diff --git a/composer.json b/composer.json
index 0b1ccaa1..f2437f06 100644
--- a/composer.json
+++ b/composer.json
@@ -25,12 +25,14 @@
         }
     },
     "require": {
-        "php": "^5.6 || ^7.0",
-        "laminas/laminas-zendframework-bridge": "^1.0"
+        "php": "^7.3 || ~8.0.0",
+        "ext-dom": "*",
+        "ext-libxml": "*",
+        "laminas/laminas-zendframework-bridge": "^1.1"
     },
     "require-dev": {
         "laminas/laminas-coding-standard": "~1.0.0",
-        "phpunit/phpunit": "^5.7.23 || ^6.4.3"
+        "phpunit/phpunit": "^9.4.3"
     },
     "autoload": {
         "psr-4": {
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 9fbc2cf8..93d33cc0 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,17 +1,16 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
-         bootstrap="vendor/autoload.php"
-         colors="true">
-    <testsuites>
-        <testsuite name="laminas-dom Test Suite">
-            <directory>./test</directory>
-        </testsuite>
-    </testsuites>
-
-    <filter>
-        <whitelist processUncoveredFilesFromWhitelist="true">
-            <directory suffix=".php">./src</directory>
-        </whitelist>
-    </filter>
+        xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+        bootstrap="vendor/autoload.php"
+        colors="true">
+  <coverage processUncoveredFiles="true">
+    <include>
+      <directory suffix=".php">./src</directory>
+    </include>
+  </coverage>
+  <testsuites>
+    <testsuite name="laminas-dom Test Suite">
+      <directory>./test</directory>
+    </testsuite>
+  </testsuites>
 </phpunit>
diff --git a/src/Document.php b/src/Document.php
index e403095c..41d6b24b 100644
--- a/src/Document.php
+++ b/src/Document.php
@@ -231,7 +231,7 @@ protected function setErrors($errors)
     protected function getDomDocumentFromString($stringDocument)
     {
         libxml_use_internal_errors(true);
-        libxml_disable_entity_loader(true);
+        $disableEntityLoaderFlag = self::disableEntityLoader();
 
         $encoding  = $this->getEncoding();
         $domDoc    = null === $encoding ? new DOMDocument('1.0') : new DOMDocument('1.0', $encoding);
@@ -261,7 +261,7 @@ protected function getDomDocumentFromString($stringDocument)
             libxml_clear_errors();
         }
 
-        libxml_disable_entity_loader(false);
+        self::disableEntityLoader($disableEntityLoaderFlag);
         libxml_use_internal_errors(false);
 
         if (! $success) {
@@ -311,4 +311,22 @@ public function registerXpathPhpFunctions($xpathPhpFunctions = true)
     {
         $this->xpathPhpFunctions = $xpathPhpFunctions;
     }
+
+    /**
+     * Disable the ability to load external XML entities based on libxml version
+     *
+     * If we are using libxml < 2.9, unsafe XML entity loading must be
+     * disabled with a flag.
+     *
+     * If we are using libxml >= 2.9, XML entity loading is disabled by default.
+     *
+     * @return bool
+     */
+    private static function disableEntityLoader($flag = true)
+    {
+        if (LIBXML_VERSION < 20900) {
+            return libxml_disable_entity_loader($flag);
+        }
+        return $flag;
+    }
 }
diff --git a/src/Query.php b/src/Query.php
index b6bb7915..ecbff610 100644
--- a/src/Query.php
+++ b/src/Query.php
@@ -232,7 +232,7 @@ public function queryXpath($xpathQuery, $query = null, DOMNode $contextNode = nu
 
         $encoding = $this->getEncoding();
         libxml_use_internal_errors(true);
-        libxml_disable_entity_loader(true);
+        $disableEntityLoaderFlag = self::disableEntityLoader();
         if (null === $encoding) {
             $domDoc = new DOMDocument('1.0');
         } else {
@@ -261,7 +261,7 @@ public function queryXpath($xpathQuery, $query = null, DOMNode $contextNode = nu
             $this->documentErrors = $errors;
             libxml_clear_errors();
         }
-        libxml_disable_entity_loader(false);
+        self::disableEntityLoader($disableEntityLoaderFlag);
         libxml_use_internal_errors(false);
 
         if (! $success) {
@@ -320,4 +320,22 @@ protected function getNodeList($document, $xpathQuery, DOMNode $contextNode = nu
         $nodeList = $xpath->queryWithErrorException($xpathQuery, $contextNode);
         return $nodeList;
     }
+
+    /**
+     * Disable the ability to load external XML entities based on libxml version
+     *
+     * If we are using libxml < 2.9, unsafe XML entity loading must be
+     * disabled with a flag.
+     *
+     * If we are using libxml >= 2.9, XML entity loading is disabled by default.
+     *
+     * @return bool
+     */
+    private static function disableEntityLoader($flag = true)
+    {
+        if (LIBXML_VERSION < 20900) {
+            return libxml_disable_entity_loader($flag);
+        }
+        return $flag;
+    }
 }
diff --git a/test/DOMXPathTest.php b/test/DOMXPathTest.php
index 11674e4a..ead689d4 100644
--- a/test/DOMXPathTest.php
+++ b/test/DOMXPathTest.php
@@ -19,7 +19,7 @@ class DOMXPathTest extends TestCase
     /** @var DOMDocument */
     private $document;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         $this->document = new DOMDocument('<any></any>');
     }
diff --git a/test/Document/NodeListTest.php b/test/Document/NodeListTest.php
index 143d3173..56386dba 100644
--- a/test/Document/NodeListTest.php
+++ b/test/Document/NodeListTest.php
@@ -26,7 +26,7 @@ class NodeListTest extends TestCase
     /** @var NodeList|DOMNode[] */
     private $nodeList;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         $document = new DOMDocument();
         $document->loadHTML('<html><body><a></a><b></b></body></html>');
diff --git a/test/Document/QueryTest.php b/test/Document/QueryTest.php
index d134ad7b..1ec576e5 100644
--- a/test/Document/QueryTest.php
+++ b/test/Document/QueryTest.php
@@ -19,7 +19,7 @@ class QueryTest extends TestCase
     public function testTransformShouldReturnStringByDefault()
     {
         $test = Query::cssToXpath('');
-        $this->assertInternalType('string', $test);
+        $this->assertIsString($test);
     }
 
     /**
@@ -28,8 +28,8 @@ public function testTransformShouldReturnStringByDefault()
     public function testTransformShouldReturnMultiplePathsWhenExpressionContainsCommas()
     {
         $test = Query::cssToXpath('#foo, #bar');
-        $this->assertInternalType('string', $test);
-        $this->assertContains('|', $test);
+        $this->assertIsString($test);
+        $this->assertStringContainsString('|', $test);
         $this->assertCount(2, explode('|', $test));
     }
 
@@ -48,13 +48,13 @@ public function testTransformShouldRecognizeDotSymbolAsClass()
     public function testTransformShouldAssumeSpacesToIndicateRelativeXpathQueries()
     {
         $test = Query::cssToXpath('div#foo .bar');
-        $this->assertContains('|', $test);
+        $this->assertStringContainsString('|', $test);
         $expected = [
             "//div[@id='foo']//*[contains(concat(' ', normalize-space(@class), ' '), ' bar ')]",
             "//div[@id='foo'][contains(concat(' ', normalize-space(@class), ' '), ' bar ')]",
         ];
         foreach ($expected as $path) {
-            $this->assertContains($path, $test);
+            $this->assertStringContainsString($path, $test);
         }
     }
 
@@ -70,8 +70,8 @@ public function testTransformShouldWriteChildSelectorsAsAbsoluteXpathRelations()
     public function testMultipleComplexCssSpecificationShouldTransformToExpectedXpath()
     {
         $test = Query::cssToXpath('div#foo span.bar, #bar li.baz a');
-        $this->assertInternalType('string', $test);
-        $this->assertContains('|', $test);
+        $this->assertIsString($test);
+        $this->assertStringContainsString('|', $test);
         $actual   = explode('|', $test);
         $expected = [
             "//div[@id='foo']//span[contains(concat(' ', normalize-space(@class), ' '), ' bar ')]",
@@ -86,7 +86,7 @@ public function testMultipleComplexCssSpecificationShouldTransformToExpectedXpat
     public function testClassNotationWithoutSpecifiedTagShouldResultInMultipleQueries()
     {
         $test = Query::cssToXpath('div.foo .bar a .baz span');
-        $this->assertContains('|', $test);
+        $this->assertStringContainsString('|', $test);
         // @codingStandardsIgnoreStart
         $segments = [
             "//div[contains(concat(' ', normalize-space(@class), ' '), ' foo ')]//*[contains(concat(' ', normalize-space(@class), ' '), ' bar ')]//a//*[contains(concat(' ', normalize-space(@class), ' '), ' baz ')]//span",
@@ -96,7 +96,7 @@ public function testClassNotationWithoutSpecifiedTagShouldResultInMultipleQuerie
         ];
         // @codingStandardsIgnoreEnd
         foreach ($segments as $xpath) {
-            $this->assertContains($xpath, $test);
+            $this->assertStringContainsString($xpath, $test);
         }
     }
 
diff --git a/test/DocumentTest.php b/test/DocumentTest.php
index 22273847..d9f6ef8b 100644
--- a/test/DocumentTest.php
+++ b/test/DocumentTest.php
@@ -29,10 +29,8 @@ class DocumentTest extends TestCase
     /**
      * Sets up the fixture, for example, open a network connection.
      * This method is called before a test is executed.
-     *
-     * @return void
      */
-    public function setUp()
+    public function setUp(): void
     {
         $this->document = new Document();
     }
@@ -233,17 +231,15 @@ public function testXpathPhpFunctionsShouldBeEnabledWithoutParameter()
     public function testXpathPhpFunctionsShouldBeNotCalledWhenSpecifiedFunction()
     {
         $this->loadHtml();
-        try {
-            $this->document->registerXpathPhpFunctions('stripos');
-            $result = Document\Query::execute(
-                '//meta[php:functionString("strtolower", @http-equiv) = "content-type"]',
-                $this->document
-            );
-        } catch (\Exception $e) {
-            // $e->getMessage() - Not allowed to call handler 'strtolower()
-            return;
-        }
-        $this->fail('Not allowed to call handler strtolower()');
+        $this->document->registerXpathPhpFunctions('stripos');
+
+        $this->expectException(PHP_VERSION_ID >= 80000 ? \Error::class : \ErrorException::class);
+        $this->expectExceptionMessageMatches('/Not allowed to call handler .strtolower()/');
+
+        Document\Query::execute(
+            '//meta[php:functionString("strtolower", @http-equiv) = "content-type"]',
+            $this->document
+        );
     }
 
     /**
@@ -255,7 +251,7 @@ public function testLoadingDocumentWithErrorsShouldNotRaisePhpErrors()
         $this->document = new Document($file);
         $result = Document\Query::execute('p', $this->document, Document\Query::TYPE_CSS);
         $errors = $this->document->getErrors();
-        $this->assertInternalType('array', $errors);
+        $this->assertIsArray($errors);
         $this->assertNotEmpty($errors);
     }