diff --git a/package_manager/tests/src/Kernel/DiskSpaceValidatorTest.php b/package_manager/tests/src/Kernel/DiskSpaceValidatorTest.php
index 75def576670e91cfdc36ac0fe57455077d5b56bb..8e3a46c306806fc7b3d329b5497001b1c4d5ae79 100644
--- a/package_manager/tests/src/Kernel/DiskSpaceValidatorTest.php
+++ b/package_manager/tests/src/Kernel/DiskSpaceValidatorTest.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\Tests\package_manager\Kernel;
 
+use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\package_manager\Event\PreCreateEvent;
 use Drupal\package_manager\EventSubscriber\DiskSpaceValidator;
 use Drupal\package_manager\ValidationResult;
@@ -14,6 +15,18 @@ use Drupal\Component\Utility\Bytes;
  */
 class DiskSpaceValidatorTest extends PackageManagerKernelTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  public function register(ContainerBuilder $container) {
+    parent::register($container);
+
+    // Replace the validator under test with a mocked version which can be
+    // rigged up to return specific values for various filesystem checks.
+    $container->getDefinition('package_manager.validator.disk_space')
+      ->setClass(TestDiskSpaceValidator::class);
+  }
+
   /**
    * Data provider for ::testDiskSpaceValidation().
    *
@@ -142,53 +155,13 @@ class DiskSpaceValidatorTest extends PackageManagerKernelTestBase {
   public function testDiskSpaceValidation(bool $shared_disk, array $free_space, array $expected_results): void {
     $path_locator = $this->prophesize('\Drupal\package_manager\PathLocator');
     $path_locator->getProjectRoot()->willReturn('root');
+    $path_locator->getActiveDirectory()->willReturn('root');
+    $path_locator->getStageDirectory()->willReturn('/fake/stage/dir');
     $path_locator->getVendorDirectory()->willReturn('vendor');
+    $this->container->set('package_manager.path_locator', $path_locator->reveal());
 
-    // Create a mocked version of the validator which can be rigged up to return
-    // specific values for various filesystem checks.
-    $validator = new class (
-      $path_locator->reveal(),
-      $this->container->get('string_translation')
-    ) extends DiskSpaceValidator {
-
-      /**
-       * Whether the root and vendor directories are on the same logical disk.
-       *
-       * @var bool
-       */
-      public $sharedDisk;
-
-      /**
-       * The amount of free space, keyed by location.
-       *
-       * @var float[]
-       */
-      public $freeSpace = [];
-
-      /**
-       * {@inheritdoc}
-       */
-      protected function stat(string $path): array {
-        return [
-          'dev' => $this->sharedDisk ? 'disk' : uniqid(),
-        ];
-      }
-
-      /**
-       * {@inheritdoc}
-       */
-      protected function freeSpace(string $path): float {
-        return $this->freeSpace[$path];
-      }
-
-      /**
-       * {@inheritdoc}
-       */
-      protected function temporaryDirectory(): string {
-        return 'temp';
-      }
-
-    };
+    /** @var \Drupal\Tests\package_manager\Kernel\TestDiskSpaceValidator $validator */
+    $validator = $this->container->get('package_manager.validator.disk_space');
     $validator->sharedDisk = $shared_disk;
     $validator->freeSpace = array_map([Bytes::class, 'toNumber'], $free_space);
 
@@ -196,3 +169,47 @@ class DiskSpaceValidatorTest extends PackageManagerKernelTestBase {
   }
 
 }
+
+/**
+ * A test version of the disk space validator.
+ */
+class TestDiskSpaceValidator extends DiskSpaceValidator {
+
+  /**
+   * Whether the root and vendor directories are on the same logical disk.
+   *
+   * @var bool
+   */
+  public $sharedDisk;
+
+  /**
+   * The amount of free space, keyed by location.
+   *
+   * @var float[]
+   */
+  public $freeSpace = [];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function stat(string $path): array {
+    return [
+      'dev' => $this->sharedDisk ? 'disk' : uniqid(),
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function freeSpace(string $path): float {
+    return $this->freeSpace[$path];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function temporaryDirectory(): string {
+    return 'temp';
+  }
+
+}
diff --git a/package_manager/tests/src/Kernel/PackageManagerKernelTestBase.php b/package_manager/tests/src/Kernel/PackageManagerKernelTestBase.php
index f1e60957871c4c9a6426bf937df9ce8f1bed4552..7e5fdfdf87165cf210ef69a7c2c057b9b9545528 100644
--- a/package_manager/tests/src/Kernel/PackageManagerKernelTestBase.php
+++ b/package_manager/tests/src/Kernel/PackageManagerKernelTestBase.php
@@ -67,6 +67,9 @@ abstract class PackageManagerKernelTestBase extends KernelTestBase {
       $stage->require(['drupal/core:9.8.1']);
       $stage->apply();
       $stage->destroy();
+
+      // If we did not get an exception, ensure we didn't expect any results.
+      $this->assertEmpty($expected_results);
     }
     catch (StageException $e) {
       $this->assertValidationResultsEqual($expected_results, $e->getResults());
@@ -74,9 +77,6 @@ abstract class PackageManagerKernelTestBase extends KernelTestBase {
       // that we can analyze it.
       $this->assertInstanceOf($event_class, $e->event);
     }
-    // If no errors are raised, we won't have asserted anything and the test
-    // will be marked as risky. To prevent that, assert an eternal truth.
-    $this->assertTrue(TRUE);
   }
 
 }
diff --git a/package_manager/tests/src/Kernel/WritableFileSystemValidatorTest.php b/package_manager/tests/src/Kernel/WritableFileSystemValidatorTest.php
index 221181f2011ddc186de7ebd68599eb5d6e0ec55e..9ba1284b2d69c58baf0e74c10126b3a1cb30b3db 100644
--- a/package_manager/tests/src/Kernel/WritableFileSystemValidatorTest.php
+++ b/package_manager/tests/src/Kernel/WritableFileSystemValidatorTest.php
@@ -32,7 +32,7 @@ class WritableFileSystemValidatorTest extends PackageManagerKernelTestBase {
     // Replace the file system permissions validator with our test-only
     // implementation.
     $container->getDefinition('package_manager.validator.file_system')
-      ->setClass(TestValidator::class);
+      ->setClass(TestWritableFileSystemValidator::class);
   }
 
   /**
@@ -124,7 +124,7 @@ class WritableFileSystemValidatorTest extends PackageManagerKernelTestBase {
 /**
  * A test version of the file system permissions validator.
  */
-class TestValidator extends WritableFileSystemValidator {
+class TestWritableFileSystemValidator extends WritableFileSystemValidator {
 
   /**
    * {@inheritdoc}