diff --git a/phpseclib/Crypt/Common/AsymmetricKey.php b/phpseclib/Crypt/Common/AsymmetricKey.php
index 30d1b4a0..06c28022 100644
--- a/phpseclib/Crypt/Common/AsymmetricKey.php
+++ b/phpseclib/Crypt/Common/AsymmetricKey.php
@@ -130,6 +130,11 @@ abstract class AsymmetricKey
     {
         self::initialize_static_variables();
 
+        $class = new \ReflectionClass(static::class);
+        if ($class->isFinal()) {
+            throw new \RuntimeException('load() should not be called from final classes (' . static::class . ')');
+        }
+
         $components = false;
         foreach (self::$plugins[static::ALGORITHM]['Keys'] as $format) {
             if (isset(self::$invisiblePlugins[static::ALGORITHM]) && in_array($format, self::$invisiblePlugins[static::ALGORITHM])) {
diff --git a/phpseclib/Crypt/DH.php b/phpseclib/Crypt/DH.php
index a387f26c..0cf0c428 100644
--- a/phpseclib/Crypt/DH.php
+++ b/phpseclib/Crypt/DH.php
@@ -82,6 +82,11 @@ abstract class DH extends AsymmetricKey
      */
     public static function createParameters(...$args): Parameters
     {
+        $class = new \ReflectionClass(static::class);
+        if ($class->isFinal()) {
+            throw new \RuntimeException('createParameters() should not be called from final classes (' . static::class . ')');
+        }
+
         $params = new Parameters();
         if (count($args) == 2 && $args[0] instanceof BigInteger && $args[1] instanceof BigInteger) {
             //if (!$args[0]->isPrime()) {
@@ -242,6 +247,11 @@ abstract class DH extends AsymmetricKey
      */
     public static function createKey(Parameters $params, int $length = 0): PrivateKey
     {
+        $class = new \ReflectionClass(static::class);
+        if ($class->isFinal()) {
+            throw new \RuntimeException('createKey() should not be called from final classes (' . static::class . ')');
+        }
+
         $one = new BigInteger(1);
         if ($length) {
             $max = $one->bitwise_leftShift($length);
@@ -380,9 +390,9 @@ abstract class DH extends AsymmetricKey
      */
     public function getParameters(): AsymmetricKey
     {
-        $type = self::validatePlugin('Keys', 'PKCS1', 'saveParameters');
+        $type = DH::validatePlugin('Keys', 'PKCS1', 'saveParameters');
 
         $key = $type::saveParameters($this->prime, $this->base);
-        return self::load($key, 'PKCS1');
+        return DH::load($key, 'PKCS1');
     }
 }
diff --git a/phpseclib/Crypt/DH/Parameters.php b/phpseclib/Crypt/DH/Parameters.php
index 958bb8f3..7e8106ed 100644
--- a/phpseclib/Crypt/DH/Parameters.php
+++ b/phpseclib/Crypt/DH/Parameters.php
@@ -20,7 +20,7 @@ use phpseclib3\Crypt\DH;
  *
  * @author  Jim Wigginton <terrafrost@php.net>
  */
-class Parameters extends DH
+final class Parameters extends DH
 {
     /**
      * Returns the parameters
diff --git a/phpseclib/Crypt/DH/PrivateKey.php b/phpseclib/Crypt/DH/PrivateKey.php
index 608d22cb..0d3089f5 100644
--- a/phpseclib/Crypt/DH/PrivateKey.php
+++ b/phpseclib/Crypt/DH/PrivateKey.php
@@ -22,7 +22,7 @@ use phpseclib3\Math\BigInteger;
  *
  * @author  Jim Wigginton <terrafrost@php.net>
  */
-class PrivateKey extends DH
+final class PrivateKey extends DH
 {
     use Common\Traits\PasswordProtected;
 
diff --git a/phpseclib/Crypt/DH/PublicKey.php b/phpseclib/Crypt/DH/PublicKey.php
index 7ffd6fab..134b39a1 100644
--- a/phpseclib/Crypt/DH/PublicKey.php
+++ b/phpseclib/Crypt/DH/PublicKey.php
@@ -22,7 +22,7 @@ use phpseclib3\Math\BigInteger;
  *
  * @author  Jim Wigginton <terrafrost@php.net>
  */
-class PublicKey extends DH
+final class PublicKey extends DH
 {
     use Common\Traits\Fingerprint;
 
diff --git a/phpseclib/Crypt/DSA.php b/phpseclib/Crypt/DSA.php
index 0094bc56..a5974718 100644
--- a/phpseclib/Crypt/DSA.php
+++ b/phpseclib/Crypt/DSA.php
@@ -106,6 +106,11 @@ abstract class DSA extends AsymmetricKey
     {
         self::initialize_static_variables();
 
+        $class = new \ReflectionClass(static::class);
+        if ($class->isFinal()) {
+            throw new \RuntimeException('createParameters() should not be called from final classes (' . static::class . ')');
+        }
+
         if (!isset(self::$engines['PHP'])) {
             self::useBestEngine();
         }
@@ -181,6 +186,11 @@ abstract class DSA extends AsymmetricKey
     {
         self::initialize_static_variables();
 
+        $class = new \ReflectionClass(static::class);
+        if ($class->isFinal()) {
+            throw new \RuntimeException('createKey() should not be called from final classes (' . static::class . ')');
+        }
+
         if (!isset(self::$engines['PHP'])) {
             self::useBestEngine();
         }
diff --git a/phpseclib/Crypt/DSA/Parameters.php b/phpseclib/Crypt/DSA/Parameters.php
index 5dc8a718..243f0de5 100644
--- a/phpseclib/Crypt/DSA/Parameters.php
+++ b/phpseclib/Crypt/DSA/Parameters.php
@@ -20,7 +20,7 @@ use phpseclib3\Crypt\DSA;
  *
  * @author  Jim Wigginton <terrafrost@php.net>
  */
-class Parameters extends DSA
+final class Parameters extends DSA
 {
     /**
      * Returns the parameters
diff --git a/phpseclib/Crypt/DSA/PrivateKey.php b/phpseclib/Crypt/DSA/PrivateKey.php
index 43a5a747..e781963a 100644
--- a/phpseclib/Crypt/DSA/PrivateKey.php
+++ b/phpseclib/Crypt/DSA/PrivateKey.php
@@ -23,7 +23,7 @@ use phpseclib3\Math\BigInteger;
  *
  * @author  Jim Wigginton <terrafrost@php.net>
  */
-class PrivateKey extends DSA implements Common\PrivateKey
+final class PrivateKey extends DSA implements Common\PrivateKey
 {
     use Common\Traits\PasswordProtected;
 
diff --git a/phpseclib/Crypt/DSA/PublicKey.php b/phpseclib/Crypt/DSA/PublicKey.php
index 5a0af509..77dc8f4a 100644
--- a/phpseclib/Crypt/DSA/PublicKey.php
+++ b/phpseclib/Crypt/DSA/PublicKey.php
@@ -22,7 +22,7 @@ use phpseclib3\Crypt\DSA\Formats\Signature\ASN1 as ASN1Signature;
  *
  * @author  Jim Wigginton <terrafrost@php.net>
  */
-class PublicKey extends DSA implements Common\PublicKey
+final class PublicKey extends DSA implements Common\PublicKey
 {
     use Common\Traits\Fingerprint;
 
diff --git a/phpseclib/Crypt/EC.php b/phpseclib/Crypt/EC.php
index 23d59241..81ff6577 100644
--- a/phpseclib/Crypt/EC.php
+++ b/phpseclib/Crypt/EC.php
@@ -142,6 +142,11 @@ abstract class EC extends AsymmetricKey
     {
         self::initialize_static_variables();
 
+        $class = new \ReflectionClass(static::class);
+        if ($class->isFinal()) {
+            throw new \RuntimeException('createKey() should not be called from final classes (' . static::class . ')');
+        }
+
         if (!isset(self::$engines['PHP'])) {
             self::useBestEngine();
         }
diff --git a/phpseclib/Crypt/EC/Parameters.php b/phpseclib/Crypt/EC/Parameters.php
index 96782865..256177bb 100644
--- a/phpseclib/Crypt/EC/Parameters.php
+++ b/phpseclib/Crypt/EC/Parameters.php
@@ -20,7 +20,7 @@ use phpseclib3\Crypt\EC;
  *
  * @author  Jim Wigginton <terrafrost@php.net>
  */
-class Parameters extends EC
+final class Parameters extends EC
 {
     /**
      * Returns the parameters
diff --git a/phpseclib/Crypt/EC/PrivateKey.php b/phpseclib/Crypt/EC/PrivateKey.php
index a104106a..99f1c05f 100644
--- a/phpseclib/Crypt/EC/PrivateKey.php
+++ b/phpseclib/Crypt/EC/PrivateKey.php
@@ -32,7 +32,7 @@ use phpseclib3\Math\BigInteger;
  *
  * @author  Jim Wigginton <terrafrost@php.net>
  */
-class PrivateKey extends EC implements Common\PrivateKey
+final class PrivateKey extends EC implements Common\PrivateKey
 {
     use Common\Traits\PasswordProtected;
 
diff --git a/phpseclib/Crypt/EC/PublicKey.php b/phpseclib/Crypt/EC/PublicKey.php
index ef394360..b6e619e4 100644
--- a/phpseclib/Crypt/EC/PublicKey.php
+++ b/phpseclib/Crypt/EC/PublicKey.php
@@ -30,7 +30,7 @@ use phpseclib3\Math\BigInteger;
  *
  * @author  Jim Wigginton <terrafrost@php.net>
  */
-class PublicKey extends EC implements Common\PublicKey
+final class PublicKey extends EC implements Common\PublicKey
 {
     use Common\Traits\Fingerprint;
 
diff --git a/phpseclib/Crypt/RSA.php b/phpseclib/Crypt/RSA.php
index dbeb352d..b38e9af3 100644
--- a/phpseclib/Crypt/RSA.php
+++ b/phpseclib/Crypt/RSA.php
@@ -299,6 +299,11 @@ abstract class RSA extends AsymmetricKey
     {
         self::initialize_static_variables();
 
+        $class = new \ReflectionClass(static::class);
+        if ($class->isFinal()) {
+            throw new \RuntimeException('createKey() should not be called from final classes (' . static::class . ')');
+        }
+
         $regSize = $bits >> 1; // divide by two to see how many bits P and Q would be
         if ($regSize > self::$smallestPrime) {
             $num_primes = floor($bits / self::$smallestPrime);
diff --git a/phpseclib/Crypt/RSA/PrivateKey.php b/phpseclib/Crypt/RSA/PrivateKey.php
index c113b247..08bcf45e 100644
--- a/phpseclib/Crypt/RSA/PrivateKey.php
+++ b/phpseclib/Crypt/RSA/PrivateKey.php
@@ -28,7 +28,7 @@ use phpseclib3\Math\BigInteger;
  *
  * @author  Jim Wigginton <terrafrost@php.net>
  */
-class PrivateKey extends RSA implements Common\PrivateKey
+final class PrivateKey extends RSA implements Common\PrivateKey
 {
     use Common\Traits\PasswordProtected;
 
diff --git a/phpseclib/Crypt/RSA/PublicKey.php b/phpseclib/Crypt/RSA/PublicKey.php
index 90d1bd4b..ef9e1247 100644
--- a/phpseclib/Crypt/RSA/PublicKey.php
+++ b/phpseclib/Crypt/RSA/PublicKey.php
@@ -32,7 +32,7 @@ use phpseclib3\Math\BigInteger;
  *
  * @author  Jim Wigginton <terrafrost@php.net>
  */
-class PublicKey extends RSA implements Common\PublicKey
+final class PublicKey extends RSA implements Common\PublicKey
 {
     use Common\Traits\Fingerprint;
 
diff --git a/tests/Functional/Net/SSH2Test.php b/tests/Functional/Net/SSH2Test.php
index 38e615e7..614af984 100644
--- a/tests/Functional/Net/SSH2Test.php
+++ b/tests/Functional/Net/SSH2Test.php
@@ -110,6 +110,7 @@ class SSH2Test extends PhpseclibFunctionalTestCase
     /**
      * @depends testPasswordLogin
      * @group github280
+     * @requires PHPUnit < 10
      */
     public function testExecWithMethodCallback(SSH2 $ssh): SSH2
     {
diff --git a/tests/PhpseclibTestCase.php b/tests/PhpseclibTestCase.php
index 0418c7d2..3418736c 100644
--- a/tests/PhpseclibTestCase.php
+++ b/tests/PhpseclibTestCase.php
@@ -99,66 +99,36 @@ abstract class PhpseclibTestCase extends TestCase
     // assertIsArray was not introduced until PHPUnit 8
     public static function assertIsArray($actual, string $message = ''): void
     {
-        if (method_exists(parent::class, 'assertIsArray')) {
-            parent::assertIsArray($actual, $message);
-            return;
-        }
-
         parent::assertInternalType('array', $actual, $message);
     }
 
     // assertIsString was not introduced until PHPUnit 8
     public static function assertIsString($actual, string $message = ''): void
     {
-        if (method_exists(parent::class, 'assertIsString')) {
-            parent::assertIsString($actual, $message);
-            return;
-        }
-
         parent::assertInternalType('string', $actual, $message);
     }
 
     // assertIsResource was not introduced until PHPUnit 8
     public static function assertIsResource($actual, string $message = ''): void
     {
-        if (method_exists(parent::class, 'assertIsResource')) {
-            parent::assertIsResource($actual, $message);
-            return;
-        }
-
         parent::assertInternalType('resource', $actual, $message);
     }
 
     // assertIsObject was not introduced until PHPUnit 8
     public static function assertIsObject($actual, string $message = ''): void
     {
-        if (method_exists(parent::class, 'assertIsObject')) {
-            parent::assertIsObject($actual, $message);
-            return;
-        }
-
         parent::assertInternalType('object', $actual, $message);
     }
 
     // assertContains is deprecated for strings in PHPUnit 8
     public static function assertStringContainsString(string $needle, string $haystack, string $message = ''): void
     {
-        if (method_exists(parent::class, 'assertStringContainsString')) {
-            parent::assertStringContainsString($needle, $haystack, $message);
-            return;
-        }
-
         parent::assertContains($needle, $haystack, $message);
     }
 
     // assertNotContains is deprecated for strings in PHPUnit 8
     public static function assertStringNotContainsString(string $needle, string $haystack, string $message = ''): void
     {
-        if (method_exists(parent::class, 'assertStringContainsString')) {
-            parent::assertStringNotContainsString($needle, $haystack, $message);
-            return;
-        }
-
         parent::assertNotContains($needle, $haystack, $message);
     }
 
@@ -167,10 +137,6 @@ abstract class PhpseclibTestCase extends TestCase
      */
     public static function assertMatchesRegularExpression(string $pattern, string $string, string $message = ''): void
     {
-        if (method_exists(parent::class, 'assertMatchesRegularExpression')) {
-            parent::assertMatchesRegularExpression($pattern, $string, $message);
-        } else {
-            parent::assertRegExp($pattern, $string, $message);
-        }
+        parent::assertRegExp($pattern, $string, $message);
     }
 }
diff --git a/tests/Unit/Crypt/HashTest.php b/tests/Unit/Crypt/HashTest.php
index e4a5fb45..821f7ca3 100644
--- a/tests/Unit/Crypt/HashTest.php
+++ b/tests/Unit/Crypt/HashTest.php
@@ -171,7 +171,7 @@ class HashTest extends PhpseclibTestCase
     }
 
     /**
-     * @dataProvider hmacData()
+     * @dataProvider hmacData
      */
     public function testHMAC($hash, $key, $message, $result): void
     {
@@ -179,7 +179,7 @@ class HashTest extends PhpseclibTestCase
     }
 
     /**
-     * @dataProvider hmacData()
+     * @dataProvider hmacData
      */
     public function testHMAC96($hash, $key, $message, $result): void
     {
@@ -372,7 +372,7 @@ class HashTest extends PhpseclibTestCase
     }
 
     /**
-     * @dataProvider hashData()
+     * @dataProvider hashData
      */
     public function testHash($hash, $message, $result): void
     {
@@ -380,7 +380,7 @@ class HashTest extends PhpseclibTestCase
     }
 
     /**
-     * @dataProvider hashData()
+     * @dataProvider hashData
      */
     public function testHash96($hash, $message, $result): void
     {
diff --git a/tests/Unit/Net/SSH2UnitTest.php b/tests/Unit/Net/SSH2UnitTest.php
index cd87b4e6..59c206fe 100644
--- a/tests/Unit/Net/SSH2UnitTest.php
+++ b/tests/Unit/Net/SSH2UnitTest.php
@@ -34,6 +34,7 @@ class SSH2UnitTest extends PhpseclibTestCase
 
     /**
      * @dataProvider formatLogDataProvider
+     * @requires PHPUnit < 10
      */
     public function testFormatLog(array $message_log, array $message_number_log, $expected): void
     {
@@ -43,6 +44,9 @@ class SSH2UnitTest extends PhpseclibTestCase
         $this->assertEquals($expected, $result);
     }
 
+    /**
+     * @requires PHPUnit < 10
+     */
     public function testGenerateIdentifier(): void
     {
         $identifier = self::callFunc($this->createSSHMock(), 'generate_identifier');
@@ -70,6 +74,9 @@ class SSH2UnitTest extends PhpseclibTestCase
         }
     }
 
+    /**
+     * @requires PHPUnit < 10
+     */
     public function testGetExitStatusIfNotConnected(): void
     {
         $ssh = $this->createSSHMock();
@@ -77,12 +84,18 @@ class SSH2UnitTest extends PhpseclibTestCase
         $this->assertFalse($ssh->getExitStatus());
     }
 
+    /**
+     * @requires PHPUnit < 10
+     */
     public function testPTYIDefaultValue(): void
     {
         $ssh = $this->createSSHMock();
         $this->assertFalse($ssh->isPTYEnabled());
     }
 
+    /**
+     * @requires PHPUnit < 10
+     */
     public function testEnablePTY(): void
     {
         $ssh = $this->createSSHMock();
@@ -94,6 +107,9 @@ class SSH2UnitTest extends PhpseclibTestCase
         $this->assertFalse($ssh->isPTYEnabled());
     }
 
+    /**
+     * @requires PHPUnit < 10
+     */
     public function testQuietModeDefaultValue(): void
     {
         $ssh = $this->createSSHMock();
@@ -101,6 +117,9 @@ class SSH2UnitTest extends PhpseclibTestCase
         $this->assertFalse($ssh->isQuietModeEnabled());
     }
 
+    /**
+     * @requires PHPUnit < 10
+     */
     public function testEnableQuietMode(): void
     {
         $ssh = $this->createSSHMock();
diff --git a/tests/make_compatible_with_phpunit7.php b/tests/make_compatible_with_phpunit7.php
new file mode 100644
index 00000000..deb68aca
--- /dev/null
+++ b/tests/make_compatible_with_phpunit7.php
@@ -0,0 +1,31 @@
+<?php
+
+/** @var iterable<SplFileInfo> $files */
+$files = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator(__DIR__));
+foreach ($files as $file) {
+    if ($file->getExtension() === 'php' && $file->getPathname() !== __FILE__) {
+        $fileContents = file_get_contents($file->getPathname());
+        if ($fileContents === false) {
+            throw new \RuntimeException('file_get_contents() failed: ' . $file->getPathname());
+        }
+        $patternToReplacementMap = [
+            '~ function setUpBeforeClass\(\)~' => ' function setUpBeforeClass(): void',
+            '~ function setUp\(\)~' => ' function setUp(): void',
+            '~ function tearDown\(\)~' => ' function tearDown(): void',
+            '~ function assertIsArray\(\$actual, \$message = \'\'\)~' => ' function _assertIsArray($actual, string $message = \'\')',
+            '~ function assertIsResource\(\$actual, \$message = \'\'\)~' => ' function _assertIsResource($actual, string $message = \'\')',
+            '~ function assertIsObject\(\$actual, \$message = \'\'\)~' => ' function _assertIsObject($actual, string $message = \'\')',
+            '~ function assertIsString\(\$actual, \$message = \'\'\)~' => ' function _assertIsString($actual, string $message = \'\')',
+            '~ function assertStringContainsString\(\$needle, \$haystack, \$message = \'\'\)~' => ' function _assertStringContainsString(string $needle, string $haystack, string $message = \'\')',
+            '~ function assertStringNotContainsString\(\$needle, \$haystack, \$message = \'\'\)~' => ' function _assertStringNotContainsString(string $needle, string $haystack, string $message = \'\')'
+        ];
+        $updatedFileContents = preg_replace(
+            array_keys($patternToReplacementMap),
+            array_values($patternToReplacementMap),
+            $fileContents
+        );
+        if (file_put_contents($file->getPathname(), $updatedFileContents) === false) {
+            throw new \RuntimeException('file_put_contents() failed: ' . $file->getPathname());
+        }
+    }
+}
diff --git a/tests/make_compatible_with_phpunit9.php b/tests/make_compatible_with_phpunit9.php
new file mode 100644
index 00000000..db04795d
--- /dev/null
+++ b/tests/make_compatible_with_phpunit9.php
@@ -0,0 +1,23 @@
+<?php
+
+/** @var iterable<SplFileInfo> $files */
+$files = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator(__DIR__));
+foreach ($files as $file) {
+    if ($file->getExtension() === 'php' && $file->getPathname() !== __FILE__) {
+        $fileContents = file_get_contents($file->getPathname());
+        if ($fileContents === false) {
+            throw new \RuntimeException('file_get_contents() failed: ' . $file->getPathname());
+        }
+        $patternToReplacementMap = [
+            '~ function assertMatchesRegularExpression\(\$pattern, \$string, \$message = \'\'\)~' => ' function _assertMatchesRegularExpression(string $pattern, string $string, string $message = \'\')',
+        ];
+        $updatedFileContents = preg_replace(
+            array_keys($patternToReplacementMap),
+            array_values($patternToReplacementMap),
+            $fileContents
+        );
+        if (file_put_contents($file->getPathname(), $updatedFileContents) === false) {
+            throw new \RuntimeException('file_put_contents() failed: ' . $file->getPathname());
+        }
+    }
+}