diff --git a/core/tests/Drupal/Tests/Core/Scripts/TestSiteApplicationTest.php b/core/tests/Drupal/Tests/Core/Scripts/TestSiteApplicationTest.php
index 21104a3341..2417b88797 100644
--- a/core/tests/Drupal/Tests/Core/Scripts/TestSiteApplicationTest.php
+++ b/core/tests/Drupal/Tests/Core/Scripts/TestSiteApplicationTest.php
@@ -31,13 +31,6 @@
  */
 class TestSiteApplicationTest extends UnitTestCase {
 
-  /**
-   * Environment variables for the processes run by this test.
-   *
-   * @var array
-   */
-  protected $env;
-
   /**
    * {@inheritdoc}
    */
@@ -54,10 +47,6 @@ protected function setUp() {
     if (!getenv('SIMPLETEST_DB')) {
       $this->markTestSkipped('This test requires the environment variable SIMPLETEST_DB to set. See core/phpunit.xml.dist.');
     }
-    // The SIMPLETEST_BASE_URL variable is required by FunctionalTestSetupTrait.
-    $this->env = [
-      'SIMPLETEST_BASE_URL' => getenv('SIMPLETEST_BASE_URL'),
-    ];
   }
 
   /**
@@ -72,7 +61,7 @@ public function testInstallScript() {
     $process = new Process($command_line, $this->root);
     // Set the timeout to a value that allows debugging.
     $process->setTimeout(500);
-    $process->run(NULL, $this->env);
+    $process->run();
 
     $this->assertSame(0, $process->getExitCode());
     $result = json_decode($process->getOutput(), TRUE);
@@ -101,10 +90,10 @@ public function testInstallScript() {
     // Install another site so we can ensure the tear down command only removes
     // one site at a time. Use the regular output.
     $command_line = $php_binary_path . ' core/scripts/test-site.php install --setup-file core/tests/Drupal/TestSite/TestSiteInstallTestScript.php --db-url "' . getenv('SIMPLETEST_DB') . '"';
-    $process = new Process($command_line, $this->root, $this->env);
+    $process = new Process($command_line, $this->root);
     // Set the timeout to a value that allows debugging.
     $process->setTimeout(500);
-    $process->run(NULL, $this->env);
+    $process->run();
     $this->assertContains('Successfully installed a test site', $process->getOutput());
     $this->assertSame(0, $process->getExitCode());
     $regex = '/Database prefix\s+([^\s]*)/';
@@ -119,10 +108,10 @@ public function testInstallScript() {
 
     // Now test the tear down process as well, but keep the lock.
     $command_line = $php_binary_path . ' core/scripts/test-site.php tear-down ' . $db_prefix . ' --keep-lock --db-url "' . getenv('SIMPLETEST_DB') . '"';
-    $process = new Process($command_line, $this->root, $this->env);
+    $process = new Process($command_line, $this->root);
     // Set the timeout to a value that allows debugging.
     $process->setTimeout(500);
-    $process->run(NULL, $this->env);
+    $process->run();
     $this->assertSame(0, $process->getExitCode());
     $this->assertContains("Successfully uninstalled $db_prefix test site", $process->getOutput());
 
@@ -142,10 +131,10 @@ public function testInstallScript() {
     $test_site_settings = $this->root . DIRECTORY_SEPARATOR . $test_database->getTestSitePath() . DIRECTORY_SEPARATOR . 'settings.php';
     $this->assertTrue(unlink($test_site_settings));
     $command_line = $php_binary_path . ' core/scripts/test-site.php tear-down ' . $other_db_prefix . ' --db-url "' . getenv('SIMPLETEST_DB') . '"';
-    $process = new Process($command_line, $this->root, $this->env);
+    $process = new Process($command_line, $this->root);
     // Set the timeout to a value that allows debugging.
     $process->setTimeout(500);
-    $process->run(NULL, $this->env);
+    $process->run();
     $this->assertSame(0, $process->getExitCode());
     $this->assertContains("Successfully uninstalled $other_db_prefix test site", $process->getOutput());
 
@@ -175,9 +164,9 @@ public function testInstallInDifferentLanguage() {
     $php_binary_path = $php_binary_finder->find();
 
     $command_line = $php_binary_path . ' core/scripts/test-site.php install --json --langcode fr --setup-file core/tests/Drupal/TestSite/TestSiteInstallTestScript.php --db-url "' . getenv('SIMPLETEST_DB') . '"';
-    $process = new Process($command_line, $this->root, $this->env);
+    $process = new Process($command_line, $this->root);
     $process->setTimeout(500);
-    $process->run(NULL, $this->env);
+    $process->run();
     $this->assertEquals(0, $process->getExitCode());
 
     $result = json_decode($process->getOutput(), TRUE);
@@ -193,9 +182,9 @@ public function testInstallInDifferentLanguage() {
 
     // Now test the tear down process as well.
     $command_line = $php_binary_path . ' core/scripts/test-site.php tear-down ' . $db_prefix . ' --db-url "' . getenv('SIMPLETEST_DB') . '"';
-    $process = new Process($command_line, $this->root, $this->env);
+    $process = new Process($command_line, $this->root);
     $process->setTimeout(500);
-    $process->run(NULL, $this->env);
+    $process->run();
     $this->assertSame(0, $process->getExitCode());
 
     // Ensure that all the tables for this DB prefix are gone.
@@ -211,9 +200,9 @@ public function testTearDownDbPrefixValidation() {
     $php_binary_path = $php_binary_finder->find();
 
     $command_line = $php_binary_path . ' core/scripts/test-site.php tear-down not-a-valid-prefix';
-    $process = new Process($command_line, $this->root, $this->env);
+    $process = new Process($command_line, $this->root);
     $process->setTimeout(500);
-    $process->run(NULL, $this->env);
+    $process->run();
     $this->assertSame(1, $process->getExitCode());
     $this->assertContains('Invalid database prefix: not-a-valid-prefix', $process->getErrorOutput());
   }