diff --git a/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php b/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php
index 92f8cad759..3d236f4869 100644
--- a/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php
+++ b/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php
@@ -35,7 +35,7 @@ class TestSiteInstallCommand extends Command {
    *
    * @var string
    */
-  protected $profile;
+  protected $profile = 'testing';
 
   /**
    * Time limit in seconds for the test.
@@ -70,7 +70,7 @@ protected function configure() {
       ->addOption('db_url', NULL, InputOption::VALUE_OPTIONAL, 'URL for database or SIMPLETEST_DB', getenv('SIMPLETEST_DB'))
       ->addOption('base_url', NULL, InputOption::VALUE_OPTIONAL, 'Base URL for site under test or SIMPLETEST_BASE_URL', getenv('SIMPLETEST_BASE_URL'))
       ->addOption('install_profile', NULL, InputOption::VALUE_OPTIONAL, 'Install profile to install the site in. Defaults to testing', 'testing')
-      ->addOption('langcode', NULL, InputOption::VALUE_OPTIONAL, 'The language to install the site in.')
+      ->addOption('langcode', NULL, InputOption::VALUE_OPTIONAL, 'The language to install the site in. Defaults to en', 'en')
       ->addOption('json', NULL, InputOption::VALUE_NONE, 'Output test site connection details in JSON');
   }
 
@@ -153,7 +153,7 @@ public function setup($profile = 'testing', $setup_class = NULL, $langcode = 'en
   }
 
   /**
-   * Installs Drupal into the Simpletest site.
+   * Installs Drupal into the test site.
    */
   protected function installDrupal() {
     $this->initUserSession();
diff --git a/core/tests/Drupal/TestSite/TestSiteApplication.php b/core/tests/Drupal/TestSite/TestSiteApplication.php
index 8ab17fc6a4..02359fbf64 100644
--- a/core/tests/Drupal/TestSite/TestSiteApplication.php
+++ b/core/tests/Drupal/TestSite/TestSiteApplication.php
@@ -26,7 +26,7 @@ class TestSiteApplication extends Application {
   /**
    * TestSiteApplication constructor.
    *
-   * @param string $autoloader
+   * @param object $autoloader
    *   The used PHP autoloader.
    */
   public function __construct($autoloader) {
diff --git a/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php b/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php
index ba57860cc2..b93e9d5f32 100644
--- a/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php
+++ b/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php
@@ -40,51 +40,51 @@ protected function setUp() {
    * @coversNothing
    */
   public function testInstallWithNonExistingClass() {
-    $phpBinaryFinder = new PhpExecutableFinder();
-    $phpBinaryPath = $phpBinaryFinder->find();
+    $php_binary_finder = new PhpExecutableFinder();
+    $php_binary_path = $php_binary_finder->find();
 
     // Create a connection to the DB configured in SIMPLETEST_DB.
     $connection = Database::getConnection('default', $this->addTestDatabase(''));
     $table_count = count($connection->schema()->findTables('%'));
 
-    $command_line = $phpBinaryPath . ' core/scripts/test-site.php install --setup_class "this-class-does-not-exist" --db_url "' . getenv('SIMPLETEST_DB') . '"';
+    $command_line = $php_binary_path . ' core/scripts/test-site.php install --setup_class "this-class-does-not-exist" --db_url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root);
     $process->run();
 
     $this->assertContains('There was a problem loading this-class-does-not-exist', $process->getErrorOutput());
     $this->assertSame(1, $process->getExitCode());
-    $this->assertSame($table_count, count($connection->schema()->findTables('%')), 'No additional tables created in the database');
+    $this->assertCount($table_count, $connection->schema()->findTables('%'), 'No additional tables created in the database');
   }
 
   /**
    * @coversNothing
    */
   public function testInstallWithNonSetupClass() {
-    $phpBinaryFinder = new PhpExecutableFinder();
-    $phpBinaryPath = $phpBinaryFinder->find();
+    $php_binary_finder = new PhpExecutableFinder();
+    $php_binary_path = $php_binary_finder->find();
 
     // Create a connection to the DB configured in SIMPLETEST_DB.
     $connection = Database::getConnection('default', $this->addTestDatabase(''));
     $table_count = count($connection->schema()->findTables('%'));
 
-    $command_line = $phpBinaryPath . ' core/scripts/test-site.php install --setup_class "' . static::class . '" --db_url "' . getenv('SIMPLETEST_DB') . '"';
+    $command_line = $php_binary_path . ' core/scripts/test-site.php install --setup_class "' . static::class . '" --db_url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root);
     $process->run();
 
     $this->assertContains('You need to define a class implementing \Drupal\TestSite\TestSetupInterface', $process->getErrorOutput());
     $this->assertSame(1, $process->getExitCode());
-    $this->assertSame($table_count, count($connection->schema()->findTables('%')), 'No additional tables created in the database');
+    $this->assertCount($table_count, $connection->schema()->findTables('%'), 'No additional tables created in the database');
   }
 
   /**
    * @coversNothing
    */
   public function testInstallScript() {
-    $phpBinaryFinder = new PhpExecutableFinder();
-    $phpBinaryPath = $phpBinaryFinder->find();
+    $php_binary_finder = new PhpExecutableFinder();
+    $php_inary_path = $php_binary_finder->find();
 
     // Install a site using the JSON output.
-    $command_line = $phpBinaryPath . ' core/scripts/test-site.php install --json --setup_class "' . TestSiteInstallTestScript::class . '" --db_url "' . getenv('SIMPLETEST_DB') . '"';
+    $command_line = $php_inary_path . ' core/scripts/test-site.php install --json --setup_class "' . TestSiteInstallTestScript::class . '" --db_url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root);
     // Set the timeout to a value that allows debugging.
     $process->setTimeout(500);
@@ -113,7 +113,7 @@ public function testInstallScript() {
 
     // Install another site so we can ensure tear down only removes one site at
     // a time. Use the regular output.
-    $command_line = $phpBinaryPath . ' core/scripts/test-site.php install --setup_class "' . TestSiteInstallTestScript::class . '" --db_url "' . getenv('SIMPLETEST_DB') . '"';
+    $command_line = $php_inary_path . ' core/scripts/test-site.php install --setup_class "' . TestSiteInstallTestScript::class . '" --db_url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root);
     // Set the timeout to a value that allows debugging.
     $process->setTimeout(500);
@@ -128,7 +128,7 @@ public function testInstallScript() {
     $this->assertGreaterThan(0, count(Database::getConnection('default', $other_key)->schema()->findTables('%')));
 
     // Now test the tear down process as well.
-    $command_line = $phpBinaryPath . ' core/scripts/test-site.php tear-down ' . $db_prefix . ' --db_url "' . getenv('SIMPLETEST_DB') . '"';
+    $command_line = $php_inary_path . ' core/scripts/test-site.php tear-down ' . $db_prefix . ' --db_url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root);
     // Set the timeout to a value that allows debugging.
     $process->setTimeout(500);
@@ -147,7 +147,7 @@ public function testInstallScript() {
     $this->assertFileExists($test_file);
 
     // Tear down the other site installed.
-    $command_line = $phpBinaryPath . ' core/scripts/test-site.php tear-down ' . $other_db_prefix . ' --db_url "' . getenv('SIMPLETEST_DB') . '"';
+    $command_line = $php_inary_path . ' core/scripts/test-site.php tear-down ' . $other_db_prefix . ' --db_url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root);
     // Set the timeout to a value that allows debugging.
     $process->setTimeout(500);
@@ -164,10 +164,10 @@ public function testInstallScript() {
    * @coversNothing
    */
   public function testInstallInDifferentLanguage() {
-    $phpBinaryFinder = new PhpExecutableFinder();
-    $phpBinaryPath = $phpBinaryFinder->find();
+    $php_binary_finder = new PhpExecutableFinder();
+    $php_binary_path = $php_binary_finder->find();
 
-    $command_line = $phpBinaryPath . ' core/scripts/test-site.php install --json --langcode fr --setup_class "' . TestSiteInstallTestScript::class . '" --db_url "' . getenv('SIMPLETEST_DB') . '"';
+    $command_line = $php_binary_path . ' core/scripts/test-site.php install --json --langcode fr --setup_class "' . TestSiteInstallTestScript::class . '" --db_url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root);
     $process->setTimeout(500);
     $process->run();
@@ -185,7 +185,7 @@ public function testInstallInDifferentLanguage() {
     $this->assertContains('lang="fr"', (string) $response->getBody());
 
     // Now test the tear down process as well.
-    $command_line = $phpBinaryPath . ' core/scripts/test-site.php tear-down ' . $db_prefix . ' --db_url "' . getenv('SIMPLETEST_DB') . '"';
+    $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);
     $process->setTimeout(500);
     $process->run();
@@ -198,7 +198,7 @@ public function testInstallInDifferentLanguage() {
   /**
    * Adds the installed test site to the database connection info.
    *
-   * @param $db_prefix
+   * @param string $db_prefix
    *   The prefix of the installed test site.
    *
    * @return string