diff --git a/core/modules/path/lib/Drupal/path/Tests/PathAliasTest.php b/core/modules/path/lib/Drupal/path/Tests/PathAliasTest.php
index e97101d..b55086b 100644
--- a/core/modules/path/lib/Drupal/path/Tests/PathAliasTest.php
+++ b/core/modules/path/lib/Drupal/path/Tests/PathAliasTest.php
@@ -7,17 +7,12 @@
 
 namespace Drupal\path\Tests;
 
+use Drupal\simpletest\SingleEnvInterface;
+
 /**
  * Tests path alias functionality.
  */
-class PathAliasTest extends PathTestBase {
-
-  /**
-   * Modules to enable.
-   *
-   * @var array
-   */
-  public static $modules = array('path');
+class PathAliasTest extends PathTestBase implements SingleEnvInterface {
 
   public static function getInfo() {
     return array(
@@ -27,8 +22,8 @@ public static function getInfo() {
     );
   }
 
-  function setUp() {
-    parent::setUp();
+  function setUpBeforeClass() {
+    parent::setUpBeforeClass();
 
     // Create test user and login.
     $web_user = $this->drupalCreateUser(array('create page content', 'edit own page content', 'administer url aliases', 'create url aliases'));
diff --git a/core/modules/path/lib/Drupal/path/Tests/PathTestBase.php b/core/modules/path/lib/Drupal/path/Tests/PathTestBase.php
index 97f3f81..b4e71d6 100644
--- a/core/modules/path/lib/Drupal/path/Tests/PathTestBase.php
+++ b/core/modules/path/lib/Drupal/path/Tests/PathTestBase.php
@@ -8,6 +8,7 @@
 namespace Drupal\path\Tests;
 
 use Drupal\simpletest\WebTestBase;
+use Drupal\simpletest\SingleEnvInterface;
 
 /**
  * Provides a base class for testing the Path module.
@@ -21,9 +22,21 @@
    */
   public static $modules = array('node', 'path');
 
+  function setUpBeforeClass() {
+    parent::setUpBeforeClass();
+    if ($this instanceof SingleEnvInterface) {
+      $this->doSetUp();
+    }
+  }
+
   function setUp() {
     parent::setUp();
+    if (!$this instanceof SingleEnvInterface) {
+      $this->doSetUp();
+    }
+  }
 
+  private function doSetUp() {
     // Create Basic page and Article node types.
     if ($this->profile != 'standard') {
       $this->drupalCreateContentType(array('type' => 'page', 'name' => 'Basic page'));
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/SingleEnvInterface.php b/core/modules/simpletest/lib/Drupal/simpletest/SingleEnvInterface.php
new file mode 100644
index 0000000..d1ccf9a
--- /dev/null
+++ b/core/modules/simpletest/lib/Drupal/simpletest/SingleEnvInterface.php
@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\simpletest\SingleEnvInterface.
+ */
+
+namespace Drupal\simpletest;
+
+/**
+ * Declares that a test class supports a single environment.
+ */
+interface SingleEnvInterface {
+
+  /**
+   * Sets up test environment (once per class).
+   */
+  public function setUpBeforeClass();
+
+  /**
+   * Tears down test environment (once per class).
+   */
+  public function tearDownAfterClass();
+
+}
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
index 067030b..aa75ee9 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
@@ -801,6 +801,72 @@ public function run(array $methods = array()) {
     }
 
     set_error_handler(array($this, 'errorHandler'));
+
+    $setup_once = $this instanceof SingleEnvInterface;
+
+    if ($setup_once) {
+      // Sanity check.
+      $compatible = TRUE;
+      foreach (class_parents($this) as $parent_class) {
+        // TestBase itself is compatible.
+        if ($parent_class === __CLASS__) {
+          continue;
+        }
+        // If it implements the interface, it is compatible.
+        $implements_interface = in_array('Drupal\simpletest\SingleEnvInterface', class_implements($parent_class));
+        if ($implements_interface) {
+          continue;
+        }
+        // Base classes may choose to support both ways (like WebTestBase).
+        $has_setup = method_exists($parent_class, 'setUp');
+        $parent_method_info = new \ReflectionMethod($parent_class, 'setUpBeforeClass');
+        if ($has_setup && $parent_method_info->class === $parent_class) {
+          continue;
+        }
+        $compatible = FALSE;
+        $this->fail("$parent_class does not support SingleEnvInterface.", 'Requirements check');
+      }
+      if (!$compatible) {
+        return;
+      }
+
+      // Insert a fail record. This will be deleted on completion to ensure
+      // that testing completed.
+      $class_info = new \ReflectionClass($class);
+      $caller = array(
+        'file' => $class_info->getFileName(),
+        'line' => $class_info->getStartLine(),
+        'function' => $class,
+      );
+      $class_completion_check_id = TestBase::insertAssert($this->testId, $class, FALSE, 'The test class did not complete due to a fatal error.', 'Completion check', $caller);
+
+      try {
+        $this->prepareEnvironment();
+      }
+      catch (\Exception $e) {
+        $this->exceptionHandler($e);
+        // The prepareEnvironment() method isolates the test from the parent
+        // Drupal site by creating a random database prefix and test site
+        // directory. If this fails, a test would possibly operate in the
+        // parent site. Therefore, the entire test run for this test class
+        // has to be aborted.
+        // restoreEnvironment() cannot be called, because we do not know
+        // where exactly the environment setup failed.
+        return;
+      }
+      try {
+        $this->setUpBeforeClass();
+      }
+      catch (\Exception $e) {
+        $this->exceptionHandler($e);
+        // Abort if setUp() fails, since all test methods will fail.
+        // But ensure to clean up and restore the environment, since
+        // prepareEnvironment() succeeded.
+        $this->restoreEnvironment();
+        return;
+      }
+    }
+
     // Iterate through all the methods in this class, unless a specific list of
     // methods to run was passed.
     $test_methods = array_filter(get_class_methods($class), function ($method) {
@@ -823,19 +889,21 @@ public function run(array $methods = array()) {
       );
       $test_completion_check_id = TestBase::insertAssert($this->testId, $class, FALSE, 'The test did not complete due to a fatal error.', 'Completion check', $caller);
 
-      try {
-        $this->prepareEnvironment();
-      }
-      catch (\Exception $e) {
-        $this->exceptionHandler($e);
-        // The prepareEnvironment() method isolates the test from the parent
-        // Drupal site by creating a random database prefix and test site
-        // directory. If this fails, a test would possibly operate in the
-        // parent site. Therefore, the entire test run for this test class
-        // has to be aborted.
-        // restoreEnvironment() cannot be called, because we do not know
-        // where exactly the environment setup failed.
-        break;
+      if (!$setup_once) {
+        try {
+          $this->prepareEnvironment();
+        }
+        catch (\Exception $e) {
+          $this->exceptionHandler($e);
+          // The prepareEnvironment() method isolates the test from the parent
+          // Drupal site by creating a random database prefix and test site
+          // directory. If this fails, a test would possibly operate in the
+          // parent site. Therefore, the entire test run for this test class
+          // has to be aborted.
+          // restoreEnvironment() cannot be called, because we do not know
+          // where exactly the environment setup failed.
+          break;
+        }
       }
 
       try {
@@ -846,7 +914,9 @@ public function run(array $methods = array()) {
         // Abort if setUp() fails, since all test methods will fail.
         // But ensure to clean up and restore the environment, since
         // prepareEnvironment() succeeded.
-        $this->restoreEnvironment();
+        if (!$setup_once) {
+          $this->restoreEnvironment();
+        }
         break;
       }
       try {
@@ -864,15 +934,32 @@ public function run(array $methods = array()) {
         // it is likely that all tests will fail in the same way and a
         // failure here only results in additional test artifacts that have
         // to be manually deleted.
-        $this->restoreEnvironment();
+        if (!$setup_once) {
+          $this->restoreEnvironment();
+        }
         break;
       }
 
-      $this->restoreEnvironment();
+      if (!$setup_once) {
+        $this->restoreEnvironment();
+      }
       // Remove the test method completion check record.
       TestBase::deleteAssert($test_completion_check_id);
     }
 
+    if ($setup_once) {
+      try {
+        $this->tearDownAfterClass();
+      }
+      catch (\Exception $e) {
+        $this->exceptionHandler($e);
+      }
+      $this->restoreEnvironment();
+
+      // Remove the test class completion check record.
+      TestBase::deleteAssert($class_completion_check_id);
+    }
+
     TestServiceProvider::$currentTest = NULL;
     // Clear out the error messages and restore error handler.
     drupal_get_messages();
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
index 942ebab..c308685 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
@@ -729,6 +729,18 @@ protected function drupalLogout() {
     }
   }
 
+  public function setUpBeforeClass() {
+    if ($this instanceof SingleEnvInterface) {
+      $this->doSetUp();
+    }
+  }
+
+  protected function setUp() {
+    if (!$this instanceof SingleEnvInterface) {
+      $this->doSetUp();
+    }
+  }
+
   /**
    * Sets up a Drupal site for running functional and integration tests.
    *
@@ -744,7 +756,7 @@ protected function drupalLogout() {
    * default values may be incompatible with the environment in which tests are
    * being executed.
    */
-  protected function setUp() {
+  private function doSetUp() {
     // When running tests through the Simpletest UI (vs. on the command line),
     // Simpletest's batch conflicts with the installer's batch. Batch API does
     // not support the concept of nested batches (in which the nested is not
@@ -1058,18 +1070,30 @@ protected function refreshVariables() {
     $this->container->get('state')->resetCache();
   }
 
+  public function tearDownAfterClass() {
+    if ($this instanceof SingleEnvInterface) {
+      $this->doTearDown();
+    }
+  }
+
+  protected function tearDown() {
+    if (!$this instanceof SingleEnvInterface) {
+      $this->doTearDown();
+    }
+    parent::tearDown();
+  }
+
   /**
    * Cleans up after testing.
    *
    * Deletes created files and temporary files directory, deletes the tables
    * created by setUp(), and resets the database prefix.
    */
-  protected function tearDown() {
+  protected function doTearDown() {
     // Destroy the testing kernel.
     if (isset($this->kernel)) {
       $this->kernel->shutdown();
     }
-    parent::tearDown();
 
     // Ensure that internal logged in variable and cURL options are reset.
     $this->loggedInUser = FALSE;