diff --git a/core/modules/system/src/Tests/Installer/InstallerSiteConfigDefaultTest.php b/core/modules/system/src/Tests/Installer/InstallerSiteConfigDefaultTest.php
deleted file mode 100644
index 1117bea095..0000000000
--- a/core/modules/system/src/Tests/Installer/InstallerSiteConfigDefaultTest.php
+++ /dev/null
@@ -1,33 +0,0 @@
-<?php
-
-namespace Drupal\system\Tests\Installer;
-
-use Drupal\simpletest\InstallerTestBase;
-
-/**
- * Verifies that the installer defaults to using the system email address and
- * timezone.
- *
- * @group Installer
- */
-class InstallerSiteConfigDefaultTest extends InstallerTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function setUpSite() {
-    $this->assertFieldByName('site_mail', ini_get('sendmail_from'));
-    $this->assertFieldByName('date_default_timezone', @date_default_timezone_get());
-
-    return parent::setUpSite();
-  }
-
-  /**
-   * Verify the correct site config was set.
-   */
-  public function testInstaller() {
-    $this->assertEqual(\Drupal::config('system.site')->get('mail'), $this->parameters['forms']['install_configure_form']['site_mail']);
-    $this->assertEqual(\Drupal::config('system.date')->get('timezone.default'), @date_default_timezone_get());
-  }
-
-}
diff --git a/core/modules/system/src/Tests/Installer/InstallerSiteConfigProfileTest.php b/core/modules/system/src/Tests/Installer/InstallerSiteConfigProfileTest.php
index 08ba200e38..945fc960e8 100644
--- a/core/modules/system/src/Tests/Installer/InstallerSiteConfigProfileTest.php
+++ b/core/modules/system/src/Tests/Installer/InstallerSiteConfigProfileTest.php
@@ -18,32 +18,18 @@ class InstallerSiteConfigProfileTest extends InstallerTestBase {
   protected $profile = 'testing_site_config';
 
   /**
-   * The site mail we expect to be set.
+   * The site mail we expect to be set from the install profile.
    *
    * @see testing_site_config_install()
    */
   const EXPECTED_SITE_MAIL = 'profile-testing-site-config@example.com';
 
   /**
-   * The timezone we expect to be set. Determined dynamically in setUpSite().
+   * The timezone we expect to be set from the install profile.
    *
    * @see testing_site_config_install()
    */
-  protected $expectedTimezone;
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function setUp() {
-    // The install profile set the timezone to one of two possibilities, but
-    // never to the system timezone. (See testing_site_config.install.)
-    $this->expectedTimezone = 'America/Los_Angeles';
-    if ($this->expectedTimezone == @date_default_timezone_get()) {
-      $this->expectedTimezone = 'America/New_York';
-    }
-
-    return parent::setUp();
-  }
+  const EXPECTED_TIMEZONE = 'America/Los_Angeles';
 
   /**
    * {@inheritdoc}
@@ -63,7 +49,7 @@ protected function installParameters() {
    */
   protected function setUpSite() {
     $this->assertFieldByName('site_mail', self::EXPECTED_SITE_MAIL);
-    $this->assertFieldByName('date_default_timezone', $this->expectedTimezone);
+    $this->assertFieldByName('date_default_timezone', self::EXPECTED_TIMEZONE);
 
     return parent::setUpSite();
   }
@@ -72,8 +58,8 @@ protected function setUpSite() {
    * Verify the correct site config was set.
    */
   public function testInstaller() {
-    $this->assertEqual(\Drupal::config('system.site')->get('mail'), self::EXPECTED_SITE_MAIL);
-    $this->assertEqual(\Drupal::config('system.date')->get('timezone.default'), $this->expectedTimezone);
+    $this->assertEqual($this->config('system.site')->get('mail'), self::EXPECTED_SITE_MAIL);
+    $this->assertEqual($this->config('system.date')->get('timezone.default'), self::EXPECTED_TIMEZONE);
   }
 
 }
diff --git a/core/modules/system/src/Tests/Installer/InstallerTest.php b/core/modules/system/src/Tests/Installer/InstallerTest.php
index be51057ad8..454e9e67ec 100644
--- a/core/modules/system/src/Tests/Installer/InstallerTest.php
+++ b/core/modules/system/src/Tests/Installer/InstallerTest.php
@@ -75,6 +75,9 @@ protected function setUpSite() {
     // Assert that the expected title is present.
     $this->assertEqual('Configure site', $this->cssSelect('main h2')[0]);
 
+    // Assert the system timezone is selected as the default.
+    $this->assertFieldByName('date_default_timezone', 'Australia/Sydney');
+
     parent::setUpSite();
   }
 
diff --git a/core/profiles/testing_site_config/testing_site_config.install b/core/profiles/testing_site_config/testing_site_config.install
index 954e4a0b66..6b6b919b0b 100644
--- a/core/profiles/testing_site_config/testing_site_config.install
+++ b/core/profiles/testing_site_config/testing_site_config.install
@@ -9,12 +9,9 @@ function testing_site_config_install() {
     ->set('mail', 'profile-testing-site-config@example.com')
     ->save(TRUE);
 
-  // Set the time zone to something that is not the system timezone.
-  $timezone = 'America/Los_Angeles';
-  if ($timezone == @date_default_timezone_get()) {
-    $timezone = 'America/New_York';
-  }
+  // Set the time zone to something that is not the system timezone (which is
+  // Australia/Sydney in the testing environment).
   \Drupal::configFactory()->getEditable('system.date')
-    ->set('timezone.default', $timezone)
+    ->set('timezone.default', 'America/Los_Angeles')
     ->save(TRUE);
 }