diff --git a/core/phpstan-baseline.neon b/core/phpstan-baseline.neon
index 42dae7ffe32..248968fa05f 100644
--- a/core/phpstan-baseline.neon
+++ b/core/phpstan-baseline.neon
@@ -2933,3 +2933,48 @@ parameters:
 			"""
 			count: 1
 			path: tests/Drupal/Tests/Listeners/DrupalListener.php
+
+		-
+			message: """
+				#^Class Drupal\\\\Tests\\\\TestSuites\\\\BuildTestSuite extends deprecated class Drupal\\\\Tests\\\\TestSuites\\\\TestSuiteBase\\:
+				in drupal\\:10\\.3\\.0 and is removed from drupal\\:11\\.0\\.0\\. There is no
+				  replacement and test discovery will be handled differently in PHPUnit 10\\.$#
+			"""
+			count: 1
+			path: tests/TestSuites/BuildTestSuite.php
+
+		-
+			message: """
+				#^Class Drupal\\\\Tests\\\\TestSuites\\\\FunctionalJavascriptTestSuite extends deprecated class Drupal\\\\Tests\\\\TestSuites\\\\TestSuiteBase\\:
+				in drupal\\:10\\.3\\.0 and is removed from drupal\\:11\\.0\\.0\\. There is no
+				  replacement and test discovery will be handled differently in PHPUnit 10\\.$#
+			"""
+			count: 1
+			path: tests/TestSuites/FunctionalJavascriptTestSuite.php
+
+		-
+			message: """
+				#^Class Drupal\\\\Tests\\\\TestSuites\\\\FunctionalTestSuite extends deprecated class Drupal\\\\Tests\\\\TestSuites\\\\TestSuiteBase\\:
+				in drupal\\:10\\.3\\.0 and is removed from drupal\\:11\\.0\\.0\\. There is no
+				  replacement and test discovery will be handled differently in PHPUnit 10\\.$#
+			"""
+			count: 1
+			path: tests/TestSuites/FunctionalTestSuite.php
+
+		-
+			message: """
+				#^Class Drupal\\\\Tests\\\\TestSuites\\\\KernelTestSuite extends deprecated class Drupal\\\\Tests\\\\TestSuites\\\\TestSuiteBase\\:
+				in drupal\\:10\\.3\\.0 and is removed from drupal\\:11\\.0\\.0\\. There is no
+				  replacement and test discovery will be handled differently in PHPUnit 10\\.$#
+			"""
+			count: 1
+			path: tests/TestSuites/KernelTestSuite.php
+
+		-
+			message: """
+				#^Class Drupal\\\\Tests\\\\TestSuites\\\\UnitTestSuite extends deprecated class Drupal\\\\Tests\\\\TestSuites\\\\TestSuiteBase\\:
+				in drupal\\:10\\.3\\.0 and is removed from drupal\\:11\\.0\\.0\\. There is no
+				  replacement and test discovery will be handled differently in PHPUnit 10\\.$#
+			"""
+			count: 1
+			path: tests/TestSuites/UnitTestSuite.php
diff --git a/core/tests/Drupal/Tests/Core/Test/PhpUnitCliTest.php b/core/tests/Drupal/Tests/Core/Test/PhpUnitCliTest.php
index 0931f20e027..a240af9d4cb 100644
--- a/core/tests/Drupal/Tests/Core/Test/PhpUnitCliTest.php
+++ b/core/tests/Drupal/Tests/Core/Test/PhpUnitCliTest.php
@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace Drupal\Tests\Core\Test;
 
 use Drupal\Tests\UnitTestCase;
+use Drupal\TestTools\PhpUnitCompatibility\RunnerVersion;
 use Symfony\Component\Process\Process;
 
 /**
@@ -15,18 +16,31 @@ class PhpUnitCliTest extends UnitTestCase {
 
   /**
    * Ensure that the test suites are able to discover tests without incident.
+   *
+   * Generate the list of tests for all the tests that PHPUnit can discover.
+   * The goal here is to successfully generate the list, without any
+   * duplicate namespace errors, deprecation errors or so forth. This keeps
+   * us from committing tests which don't break under run-tests.sh, but do
+   * break under the PHPUnit CLI test runner tool.
    */
   public function testPhpUnitListTests() {
-    // Generate the list of tests for all the tests the suites can discover.
-    // The goal here is to successfully generate the list, without any
-    // duplicate namespace errors or so forth. This keeps us from committing
-    // tests which don't break under run-tests.sh, but do break under the
-    // phpunit test runner tool.
-    $process = Process::fromShellCommandline('vendor/bin/phpunit --configuration core --verbose --list-tests');
-    $process->setWorkingDirectory($this->root)
+    $command = [
+      'vendor/bin/phpunit',
+      '--configuration',
+      'core',
+      '--list-tests',
+    ];
+
+    // PHPUnit 10 dropped the --verbose command line option.
+    if (RunnerVersion::getMajor() < 10) {
+      $command[] = '--verbose';
+    }
+
+    $process = new Process($command, $this->root);
+    $process
       ->setTimeout(300)
-      ->setIdleTimeout(300);
-    $process->run();
+      ->setIdleTimeout(300)
+      ->run();
     $this->assertEquals(0, $process->getExitCode(),
       'COMMAND: ' . $process->getCommandLine() . "\n" .
       'OUTPUT: ' . $process->getOutput() . "\n" .
diff --git a/core/tests/Drupal/Tests/Core/Test/TestSuiteBaseTest.php b/core/tests/Drupal/Tests/Core/Test/TestSuiteBaseTest.php
index 2589132ca2f..1f53f981775 100644
--- a/core/tests/Drupal/Tests/Core/Test/TestSuiteBaseTest.php
+++ b/core/tests/Drupal/Tests/Core/Test/TestSuiteBaseTest.php
@@ -7,6 +7,7 @@ namespace Drupal\Tests\Core\Test;
 use Drupal\Tests\TestSuites\TestSuiteBase;
 use org\bovigo\vfs\vfsStream;
 use PHPUnit\Framework\TestCase;
+use Symfony\Bridge\PhpUnit\ExpectDeprecationTrait;
 
 // The test suite class is not part of the autoloader, we need to include it
 // manually.
@@ -19,6 +20,8 @@ require_once __DIR__ . '/../../../../TestSuites/TestSuiteBase.php';
  */
 class TestSuiteBaseTest extends TestCase {
 
+  use ExpectDeprecationTrait;
+
   /**
    * Helper method to set up the file system.
    *
@@ -81,11 +84,16 @@ class TestSuiteBaseTest extends TestCase {
   /**
    * Tests for special case behavior of unit test suite namespaces in core.
    *
+   * @group legacy
+   *
    * @covers ::addTestsBySuiteNamespace
    *
    * @dataProvider provideCoreTests
    */
   public function testAddTestsBySuiteNamespaceCore($filesystem, $suite_namespace, $expected_tests) {
+
+    $this->expectDeprecation('Drupal\\Tests\\Core\\Test\\StubTestSuiteBase is deprecated in drupal:10.3.0 and is removed from drupal:11.0.0. There is no replacement and test discovery will be handled differently in PHPUnit 10. See https://www.drupal.org/node/3405829');
+
     // Set up the file system.
     $vfs = vfsStream::setup('root');
     vfsStream::create($filesystem, $vfs);
@@ -118,6 +126,8 @@ class TestSuiteBaseTest extends TestCase {
  *
  * We use this class to alter the behavior of TestSuiteBase so it can be
  * testable.
+ *
+ * @phpstan-ignore-next-line
  */
 class StubTestSuiteBase extends TestSuiteBase {
 
@@ -128,6 +138,12 @@ class StubTestSuiteBase extends TestSuiteBase {
    */
   public $testFiles = [];
 
+  public function __construct(string $name) {
+    @trigger_error(__CLASS__ . ' is deprecated in drupal:10.3.0 and is removed from drupal:11.0.0. There is no replacement and test discovery will be handled differently in PHPUnit 10. See https://www.drupal.org/node/3405829', E_USER_DEPRECATED);
+    // @phpstan-ignore-next-line
+    parent::__construct($name);
+  }
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/TestSuites/BuildTestSuite.php b/core/tests/TestSuites/BuildTestSuite.php
index 39c4660c7aa..c26bf44e59f 100644
--- a/core/tests/TestSuites/BuildTestSuite.php
+++ b/core/tests/TestSuites/BuildTestSuite.php
@@ -8,6 +8,11 @@ require_once __DIR__ . '/TestSuiteBase.php';
 
 /**
  * Discovers tests for the build test suite.
+ *
+ * @deprecated in drupal:10.3.0 and is removed from drupal:11.0.0. There is no
+ *   replacement and test discovery will be handled differently in PHPUnit 10.
+ *
+ * @see https://www.drupal.org/node/3405829
  */
 class BuildTestSuite extends TestSuiteBase {
 
diff --git a/core/tests/TestSuites/FunctionalJavascriptTestSuite.php b/core/tests/TestSuites/FunctionalJavascriptTestSuite.php
index d026e725e82..5ae2325121b 100644
--- a/core/tests/TestSuites/FunctionalJavascriptTestSuite.php
+++ b/core/tests/TestSuites/FunctionalJavascriptTestSuite.php
@@ -8,6 +8,11 @@ require_once __DIR__ . '/TestSuiteBase.php';
 
 /**
  * Discovers tests for the functional-javascript test suite.
+ *
+ * @deprecated in drupal:10.3.0 and is removed from drupal:11.0.0. There is no
+ *   replacement and test discovery will be handled differently in PHPUnit 10.
+ *
+ * @see https://www.drupal.org/node/3405829
  */
 class FunctionalJavascriptTestSuite extends TestSuiteBase {
 
diff --git a/core/tests/TestSuites/FunctionalTestSuite.php b/core/tests/TestSuites/FunctionalTestSuite.php
index 1ddbde2b32e..20aed98deec 100644
--- a/core/tests/TestSuites/FunctionalTestSuite.php
+++ b/core/tests/TestSuites/FunctionalTestSuite.php
@@ -8,6 +8,11 @@ require_once __DIR__ . '/TestSuiteBase.php';
 
 /**
  * Discovers tests for the functional test suite.
+ *
+ * @deprecated in drupal:10.3.0 and is removed from drupal:11.0.0. There is no
+ *   replacement and test discovery will be handled differently in PHPUnit 10.
+ *
+ * @see https://www.drupal.org/node/3405829
  */
 class FunctionalTestSuite extends TestSuiteBase {
 
diff --git a/core/tests/TestSuites/KernelTestSuite.php b/core/tests/TestSuites/KernelTestSuite.php
index 1fb4be33f4c..0916c8528fa 100644
--- a/core/tests/TestSuites/KernelTestSuite.php
+++ b/core/tests/TestSuites/KernelTestSuite.php
@@ -8,6 +8,11 @@ require_once __DIR__ . '/TestSuiteBase.php';
 
 /**
  * Discovers tests for the kernel test suite.
+ *
+ * @deprecated in drupal:10.3.0 and is removed from drupal:11.0.0. There is no
+ *   replacement and test discovery will be handled differently in PHPUnit 10.
+ *
+ * @see https://www.drupal.org/node/3405829
  */
 class KernelTestSuite extends TestSuiteBase {
 
diff --git a/core/tests/TestSuites/TestSuiteBase.php b/core/tests/TestSuites/TestSuiteBase.php
index 70ee9f7c5a1..435116d8658 100644
--- a/core/tests/TestSuites/TestSuiteBase.php
+++ b/core/tests/TestSuites/TestSuiteBase.php
@@ -9,6 +9,11 @@ use PHPUnit\Framework\TestSuite;
 
 /**
  * Base class for Drupal test suites.
+ *
+ * @deprecated in drupal:10.3.0 and is removed from drupal:11.0.0. There is no
+ *   replacement and test discovery will be handled differently in PHPUnit 10.
+ *
+ * @see https://www.drupal.org/node/3405829
  */
 abstract class TestSuiteBase extends TestSuite {
 
diff --git a/core/tests/TestSuites/UnitTestSuite.php b/core/tests/TestSuites/UnitTestSuite.php
index c24d8f85b94..db779652db4 100644
--- a/core/tests/TestSuites/UnitTestSuite.php
+++ b/core/tests/TestSuites/UnitTestSuite.php
@@ -8,6 +8,11 @@ require_once __DIR__ . '/TestSuiteBase.php';
 
 /**
  * Discovers tests for the unit test suite.
+ *
+ * @deprecated in drupal:10.3.0 and is removed from drupal:11.0.0. There is no
+ *   replacement and test discovery will be handled differently in PHPUnit 10.
+ *
+ * @see https://www.drupal.org/node/3405829
  */
 class UnitTestSuite extends TestSuiteBase {