diff --git a/src/Tests/LibrariesUnitTest.php b/src/Tests/LibrariesUnitTest.php
index 8a93c56..ef8569a 100644
--- a/src/Tests/LibrariesUnitTest.php
+++ b/src/Tests/LibrariesUnitTest.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\libraries\Tests;
 
-use Drupal\simpletest\KernelTestBase;
+use Drupal\KernelTests\KernelTestBase;
 
 /**
  * Tests basic Libraries API functions.
diff --git a/src/Tests/LibrariesWebTest.php b/src/Tests/LibrariesWebTest.php
index be28c80..bad192c 100644
--- a/src/Tests/LibrariesWebTest.php
+++ b/src/Tests/LibrariesWebTest.php
@@ -3,14 +3,14 @@
 namespace Drupal\libraries\Tests;
 
 use Drupal\Component\Utility\Html;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Tests basic detection and loading of libraries.
  *
  * @group libraries
  */
-class LibrariesWebTest extends WebTestBase {
+class LibrariesWebTest extends BrowserTestBase {
 
   /**
    * {@inheritdoc}
diff --git a/tests/modules/libraries_test/libraries_test.info.yml b/tests/modules/libraries_test/libraries_test.info.yml
index 7294032..0d5afc8 100644
--- a/tests/modules/libraries_test/libraries_test.info.yml
+++ b/tests/modules/libraries_test/libraries_test.info.yml
@@ -2,6 +2,7 @@ name: Libraries test module
 type: module
 description: Tests library detection and loading.
 core: 8.x
+core_version_requirement: ^8 || ^9
 dependencies:
   - libraries:libraries
 hidden: TRUE
diff --git a/tests/src/Functional/ExternalLibrary/Definition/DefinitionDiscoveryFactoryTest.php b/tests/src/Functional/ExternalLibrary/Definition/DefinitionDiscoveryFactoryTest.php
index 0b049bf..0fee23e 100644
--- a/tests/src/Functional/ExternalLibrary/Definition/DefinitionDiscoveryFactoryTest.php
+++ b/tests/src/Functional/ExternalLibrary/Definition/DefinitionDiscoveryFactoryTest.php
@@ -29,6 +29,13 @@ class DefinitionDiscoveryFactoryTest extends BrowserTestBase {
    */
   protected $definitionPath;
 
+  /**
+   * Set default theme to stable.
+   *
+   * @var string
+   */
+  protected $defaultTheme = 'stable';
+
   /**
    * {@inheritdoc}
    */
diff --git a/tests/src/Unit/Plugin/libraries/VersionDetector/LinePatternDetectorTest.php b/tests/src/Unit/Plugin/libraries/VersionDetector/LinePatternDetectorTest.php
index 5e4e34b..9f60071 100644
--- a/tests/src/Unit/Plugin/libraries/VersionDetector/LinePatternDetectorTest.php
+++ b/tests/src/Unit/Plugin/libraries/VersionDetector/LinePatternDetectorTest.php
@@ -5,6 +5,7 @@ namespace Drupal\Tests\libraries\Unit\Plugin\libraries\VersionDetector;
 use Drupal\libraries\ExternalLibrary\Local\LocalLibraryInterface;
 use Drupal\libraries\ExternalLibrary\Version\VersionedLibraryInterface;
 use Drupal\libraries\Plugin\libraries\VersionDetector\LinePatternDetector;
+use Drupal\libraries\ExternalLibrary\Exception\UnknownLibraryVersionException;
 use Drupal\Tests\UnitTestCase;
 use org\bovigo\vfs\vfsStream;
 
@@ -22,11 +23,10 @@ class LinePatternDetectorTest extends UnitTestCase {
   /**
    * Tests that version detection fails for a non-local library.
    *
-   * @expectedException \Drupal\libraries\ExternalLibrary\Exception\UnknownLibraryVersionException
-   *
    * @covers ::detectVersion
    */
   public function testDetectVersionNonLocal() {
+    $this->expectException(UnknownLibraryVersionException::class);
     $library = $this->prophesize(VersionedLibraryInterface::class);
     $detector = $this->setupDetector();
     $detector->detectVersion($library->reveal());
@@ -35,11 +35,10 @@ class LinePatternDetectorTest extends UnitTestCase {
   /**
    * Tests that version detection fails for a missing file.
    *
-   * @expectedException \Drupal\libraries\ExternalLibrary\Exception\UnknownLibraryVersionException
-   *
    * @covers ::detectVersion
    */
   public function testDetectVersionMissingFile() {
+    $this->expectException(UnknownLibraryVersionException::class);
     $library = $this->setupLibrary();
 
     $detector = $this->setupDetector(['file' => 'CHANGELOG.txt']);