diff --git a/core/tests/Drupal/Nightwatch/Commands/drupalCreateRole.js b/core/tests/Drupal/Nightwatch/Commands/drupalCreateRole.js
new file mode 100644
index 0000000000000000000000000000000000000000..e3903ae48755aea94ef60095a811c4878c4acca3
--- /dev/null
+++ b/core/tests/Drupal/Nightwatch/Commands/drupalCreateRole.js
@@ -0,0 +1,59 @@
+/**
+ * Creates role with given permissions.
+ *
+ * @param {object} settings
+ *   Settings object
+ * @param {array} settings.permissions
+ *   The list of roles granted for the user.
+ * @param {string} [settings.name=null]
+ *   The role name.
+ * @param {function} callback
+ *   A callback which will be called, when creating the role is finished.
+ * @return {object}
+ *   The drupalCreateRole command.
+ */
+exports.command = function drupalCreateRole({ permissions, name = null }, callback) {
+  const self = this;
+  const roleName = name || Math.random().toString(36).substring(2, 15);
+
+  let machineName;
+  this
+    .drupalLoginAsAdmin(() => {
+      this
+        .drupalRelativeURL('/admin/people/roles/add')
+        .setValue('input[name="label"]', roleName)
+        // Wait for the machine name to appear so that it can be used later to
+        // select the permissions from the permission page.
+        .expect.element('.user-role-form .machine-name-value').to.be.visible.before(2000);
+
+      this.perform((done) => {
+        this.getText('.user-role-form .machine-name-value', (element) => {
+          machineName = element.value;
+          done();
+        });
+      })
+        .submitForm('#user-role-form')
+        .drupalRelativeURL('/admin/people/permissions')
+        .perform((client, done) => {
+          Promise.all(
+            permissions.map(permission => (
+              new Promise((resolve) => {
+                client.click(`input[name="${machineName}[${permission}]"]`, () => {
+                  resolve();
+                });
+              })
+            )),
+          ).then(() => {
+            done();
+          });
+        })
+        .submitForm('#user-admin-permissions');
+    })
+    .perform(() => {
+      if (typeof callback === 'function') {
+        callback.call(self, machineName);
+      }
+    });
+
+  return this;
+};
diff --git a/core/tests/Drupal/Nightwatch/Commands/drupalCreateUser.js b/core/tests/Drupal/Nightwatch/Commands/drupalCreateUser.js
new file mode 100644
index 0000000000000000000000000000000000000000..7297cdf0c79492167bd68dbeb2a6759565ad82c1
--- /dev/null
+++ b/core/tests/Drupal/Nightwatch/Commands/drupalCreateUser.js
@@ -0,0 +1,58 @@
+/**
+ * Logs into Drupal as the given user.
+ *
+ * @param {object} settings
+ *   Settings object
+ * @param {string} settings.name
+ *   The user name.
+ * @param {string} settings.password
+ *   The user password.
+ * @param {array} [settings.permissions=[]]
+ *   The list of permissions granted for the user.
+ * @param {function} callback
+ *   A callback which will be called, when the creating the use is finished.
+ * @return {object}
+ *   The drupalCreateUser command.
+ */
+exports.command = function drupalCreateUser({ name, password, permissions = [] }, callback) {
+  const self = this;
+
+  let role;
+  this
+    .perform((client, done) => {
+      if (permissions) {
+        client.drupalCreateRole({ permissions, name: null }, (newRole) => {
+          role = newRole;
+          done();
+        });
+      }
+      else {
+        done();
+      }
+    })
+    .drupalLoginAsAdmin(() => {
+      this
+        .drupalRelativeURL('/admin/people/create')
+        .setValue('input[name="name"]', name)
+        .setValue('input[name="pass[pass1]"]', password)
+        .setValue('input[name="pass[pass2]"]', password)
+        .perform((client, done) => {
+          if (role) {
+            client.click(`input[name="roles[${role}]`, () => {
+              done();
+            });
+          }
+          else {
+            done();
+          }
+        })
+        .submitForm('#user-register-form')
+        .assert.containsText('.messages', 'Created a new user account', `User "${name}" was created succesfully.`);
+    });
+
+  if (typeof callback === 'function') {
+    callback.call(self);
+  }
+
+  return this;
+};
diff --git a/core/tests/Drupal/Nightwatch/Commands/drupalInstall.js b/core/tests/Drupal/Nightwatch/Commands/drupalInstall.js
index 2f35adfab5552bbd67a96c0b55f86a7db0e20c8e..176eeef0f00065c5bc417ebced57b6e568602867 100644
--- a/core/tests/Drupal/Nightwatch/Commands/drupalInstall.js
+++ b/core/tests/Drupal/Nightwatch/Commands/drupalInstall.js
@@ -5,16 +5,16 @@ import { commandAsWebserver } from '../globals';
 /**
  * Installs a Drupal test site.
  *
- * @param {Object}
- *   (optional) Settings object
- *   @param setupFile
- *     (optional) Setup file used by TestSiteApplicationTest
+ * @param {oject} [settings={}]
+ *   Settings object
+ * @param {string} [settings.setupFile='']
+ *   Setup file used by TestSiteApplicationTest
  * @param {function} callback
  *   A callback which will be called, when the installation is finished.
  * @return {object}
  *   The 'browser' object.
  */
-exports.command = function drupalInstall({ setupFile = '' }, callback) {
+exports.command = function drupalInstall({ setupFile = '' } = {}, callback) {
   const self = this;
 
   try {
@@ -23,6 +23,7 @@ exports.command = function drupalInstall({ setupFile = '' }, callback) {
     const install = execSync(commandAsWebserver(`php ./scripts/test-site.php install ${setupFile} --base-url ${process.env.DRUPAL_TEST_BASE_URL} ${dbOption} --json`));
     const installData = JSON.parse(install.toString());
     this.drupalDbPrefix = installData.db_prefix;
+    this.drupalSitePath = installData.site_path;
     const url = new URL(process.env.DRUPAL_TEST_BASE_URL);
     this
       .url(process.env.DRUPAL_TEST_BASE_URL)
@@ -45,5 +46,6 @@ exports.command = function drupalInstall({ setupFile = '' }, callback) {
   if (typeof callback === 'function') {
     callback.call(self);
   }
+
   return this;
 };
diff --git a/core/tests/Drupal/Nightwatch/Commands/drupalLogin.js b/core/tests/Drupal/Nightwatch/Commands/drupalLogin.js
new file mode 100644
index 0000000000000000000000000000000000000000..c6785ec814ce90483b5e8a9346347055a41fdea4
--- /dev/null
+++ b/core/tests/Drupal/Nightwatch/Commands/drupalLogin.js
@@ -0,0 +1,30 @@
+/**
+ * Logs into Drupal as the given user.
+ *
+ * @param {string} name
+ *   The user name.
+ * @param {string} password
+ *   The user password.
+ * @return {object}
+ *   The drupalUserIsLoggedIn command.
+ */
+exports.command = function drupalLogin({ name, password }) {
+  this.drupalUserIsLoggedIn((sessionExists) => {
+    // Log the current user out if necessary.
+    if (sessionExists) {
+      this.drupalLogout();
+    }
+    // Log in with the given credentials.
+    this
+      .drupalRelativeURL('/user/login')
+      .setValue('input[name="name"]', name)
+      .setValue('input[name="pass"]', password)
+      .submitForm('#user-login-form');
+    // Assert that a user is logged in.
+    this.drupalUserIsLoggedIn((sessionExists) => {
+      this.assert.equal(sessionExists, true, `The user "${name}" was logged in.`);
+    });
+  });
+
+  return this;
+};
diff --git a/core/tests/Drupal/Nightwatch/Commands/drupalLoginAsAdmin.js b/core/tests/Drupal/Nightwatch/Commands/drupalLoginAsAdmin.js
new file mode 100644
index 0000000000000000000000000000000000000000..8bc0e4e632f9370af3c70b5402020b6086db924a
--- /dev/null
+++ b/core/tests/Drupal/Nightwatch/Commands/drupalLoginAsAdmin.js
@@ -0,0 +1,37 @@
+import { execSync } from 'child_process';
+import { URL } from 'url';
+import { commandAsWebserver } from '../globals';
+
+/**
+ * Logs in as the admin user.
+ *
+ * @param {function} callback
+ *   A callback which will allow running commands as an administrator.
+ * @return {object}
+ *   The drupalLoginAsAdmin command.
+ */
+exports.command = function drupalLoginAsAdmin(callback) {
+  const self = this;
+  this.drupalUserIsLoggedIn((sessionExists) => {
+    if (sessionExists) {
+      this.drupalLogout();
+    }
+    const userLink = execSync(commandAsWebserver(`php ./scripts/test-site.php user-login 1 --site-path ${this.drupalSitePath}`));
+
+    this.drupalRelativeURL(userLink.toString());
+
+    this.drupalUserIsLoggedIn((sessionExists) => {
+      if (!sessionExists) {
+        throw new Error('Logging in as an admin user failed.');
+      }
+    });
+  });
+
+  if (typeof callback === 'function') {
+    callback.call(self);
+  }
+
+  this.drupalLogout({ silent: true });
+
+  return this;
+};
diff --git a/core/tests/Drupal/Nightwatch/Commands/drupalLogout.js b/core/tests/Drupal/Nightwatch/Commands/drupalLogout.js
new file mode 100644
index 0000000000000000000000000000000000000000..f96ce475e1584c5f750961696a0cda3d28789415
--- /dev/null
+++ b/core/tests/Drupal/Nightwatch/Commands/drupalLogout.js
@@ -0,0 +1,37 @@
+import { execSync } from 'child_process';
+import { URL } from 'url';
+
+/**
+ * Logs out from a Drupal site.
+ *
+ * @param {object} [settings={}]
+ *   The settings object.
+ * @param {boolean} [settings.silent=false]
+ *   If the command should be run silently.
+ * @param {function} callback
+ *   A callback which will be called, when the logout is finished.
+ * @return {object}
+ *   The drupalLogout command.
+ */
+exports.command = function drupalLogout({ silent = false } = {}, callback) {
+  const self = this;
+
+  this.drupalRelativeURL('/user/logout');
+
+  this.drupalUserIsLoggedIn((sessionExists) => {
+    if (silent) {
+      if (sessionExists) {
+        throw new Error('Logging out failed.');
+      }
+    }
+    else {
+      this.assert.equal(sessionExists, false, 'The user was logged out.');
+    }
+  });
+
+  if (typeof callback === 'function') {
+    callback.call(self);
+  }
+
+  return this;
+};
diff --git a/core/tests/Drupal/Nightwatch/Commands/drupalUserIsLoggedIn.js b/core/tests/Drupal/Nightwatch/Commands/drupalUserIsLoggedIn.js
new file mode 100644
index 0000000000000000000000000000000000000000..e5db1c1edd0d54c4775ffb0c863b4941ebc655fa
--- /dev/null
+++ b/core/tests/Drupal/Nightwatch/Commands/drupalUserIsLoggedIn.js
@@ -0,0 +1,19 @@
+/**
+ * Checks if a user is logged in.
+ *
+ * @param {function} callback
+ *   A callback which will be called, when the login status has been checked.
+ * @return {object}
+ *   The drupalUserIsLoggedIn command.
+ */
+exports.command = function drupalUserIsLoggedIn(callback) {
+  if (typeof callback === 'function') {
+    this.getCookies((cookies) => {
+      const sessionExists = cookies.value.some(cookie => cookie.name.match(/^SESS/));
+
+      callback.call(this, sessionExists);
+    });
+  }
+
+  return this;
+};
diff --git a/core/tests/Drupal/Nightwatch/Tests/loginTest.js b/core/tests/Drupal/Nightwatch/Tests/loginTest.js
new file mode 100644
index 0000000000000000000000000000000000000000..3c62d737c9ecec95c5186685816e2443109407d2
--- /dev/null
+++ b/core/tests/Drupal/Nightwatch/Tests/loginTest.js
@@ -0,0 +1,24 @@
+module.exports = {
+  '@tags': ['core'],
+
+  before(browser) {
+    browser
+      .drupalInstall();
+  },
+  after(browser) {
+    browser
+      .drupalUninstall();
+  },
+
+  'Test login': (browser) => {
+    browser
+      .drupalCreateUser({
+        name: 'user',
+        password: '123',
+        permissions: ['access site reports'],
+      })
+      .drupalLogin({ name: 'user', password: '123' })
+      .drupalRelativeURL('/admin/reports')
+      .expect.element('h1.page-title').text.to.contain('Reports');
+  },
+};
diff --git a/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php b/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php
index 50167bff3b2a25d887fbcae06dadc3c2f2ec969d..d020304018ab36c9ce64a1d68c322b578534ac17 100644
--- a/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php
+++ b/core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php
@@ -102,6 +102,7 @@ protected function execute(InputInterface $input, OutputInterface $output) {
       $output->writeln(json_encode([
         'db_prefix' => $this->databasePrefix,
         'user_agent' => $user_agent,
+        'site_path' => $this->siteDirectory,
       ]));
     }
     else {
@@ -110,6 +111,7 @@ protected function execute(InputInterface $input, OutputInterface $output) {
       $io->table([], [
         ['Database prefix', $this->databasePrefix],
         ['User agent', $user_agent],
+        ['Site path', $this->siteDirectory],
       ]);
     }
   }
diff --git a/core/tests/Drupal/TestSite/Commands/TestSiteUserLoginCommand.php b/core/tests/Drupal/TestSite/Commands/TestSiteUserLoginCommand.php
new file mode 100644
index 0000000000000000000000000000000000000000..55c92032cdce7198e30b94a54e2d77d1b8a3aa23
--- /dev/null
+++ b/core/tests/Drupal/TestSite/Commands/TestSiteUserLoginCommand.php
@@ -0,0 +1,71 @@
+<?php
+
+namespace Drupal\TestSite\Commands;
+
+use Drupal\Core\DrupalKernel;
+use Drupal\Core\Site\Settings;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Exception\InvalidArgumentException;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Command to generate a login link for the test site.
+ *
+ * @internal
+ */
+class TestSiteUserLoginCommand extends Command {
+
+  /**
+   * The class loader to use for installation and initialization of setup.
+   *
+   * @var \Symfony\Component\Classloader\Classloader
+   */
+  protected $classLoader;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function configure() {
+    $this->setName('user-login')
+      ->setDescription('Generate a one time login link for an user.')
+      ->addArgument('uid', InputArgument::REQUIRED, 'The ID of the user for whom the link will be generated')
+      ->addOption('site-path', NULL, InputOption::VALUE_REQUIRED, 'The path for the test site.');
+  }
+
+  /**
+   * {@inheritdoc}
+   *
+   * @throws \Symfony\Component\Console\Exception\InvalidArgumentException
+   */
+  protected function execute(InputInterface $input, OutputInterface $output) {
+    $root = dirname(dirname(dirname(dirname(dirname(__DIR__)))));
+    chdir($root);
+
+    $this->classLoader = require 'autoload.php';
+    $kernel = new DrupalKernel('prod', $this->classLoader, FALSE);
+    $kernel::bootEnvironment();
+    $kernel->setSitePath($input->getOption('site-path'));
+    Settings::initialize($kernel->getAppRoot(), $kernel->getSitePath(), $this->classLoader);
+
+    $request = Request::createFromGlobals();
+    $kernel->prepareLegacyRequest($request);
+
+    $kernel->boot();
+
+    $container = $kernel->getContainer();
+    $uid = $input->getArgument('uid');
+    if (!is_numeric($uid)) {
+      throw new InvalidArgumentException(sprintf('The "uid" argument needs to be an integer, but it is "%s".', $uid));
+    }
+    $userEntity = $container->get('entity_type.manager')
+      ->getStorage('user')
+      ->load($uid);
+    $url = user_pass_reset_url($userEntity) . '/login';
+    $output->writeln($url);
+  }
+
+}
diff --git a/core/tests/Drupal/TestSite/TestSiteApplication.php b/core/tests/Drupal/TestSite/TestSiteApplication.php
index eba29d8d3f8099f49f921afde88d693302fe4a0f..d67c4853ed8131b72cf4cc6b17884e02bc2b76a7 100644
--- a/core/tests/Drupal/TestSite/TestSiteApplication.php
+++ b/core/tests/Drupal/TestSite/TestSiteApplication.php
@@ -5,6 +5,7 @@
 use Drupal\TestSite\Commands\TestSiteInstallCommand;
 use Drupal\TestSite\Commands\TestSiteReleaseLocksCommand;
 use Drupal\TestSite\Commands\TestSiteTearDownCommand;
+use Drupal\TestSite\Commands\TestSiteUserLoginCommand;
 use Symfony\Component\Console\Application;
 
 /**
@@ -25,6 +26,7 @@ protected function getDefaultCommands() {
     $default_commands[] = new TestSiteInstallCommand();
     $default_commands[] = new TestSiteTearDownCommand();
     $default_commands[] = new TestSiteReleaseLocksCommand();
+    $default_commands[] = new TestSiteUserLoginCommand();
     return $default_commands;
   }
 
diff --git a/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php b/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php
index 50d9f99640ad363dceacd10002aff39749304e1d..d3c644468609d67413a74776879b6448cceec499 100644
--- a/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php
+++ b/core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php
@@ -28,11 +28,20 @@
  */
 class TestSiteApplicationTest extends UnitTestCase {
 
+  /**
+   * The PHP executable path.
+   *
+   * @var string
+   */
+  protected $php;
+
   /**
    * {@inheritdoc}
    */
   protected function setUp() {
     parent::setUp();
+    $php_executable_finder = new PhpExecutableFinder();
+    $this->php = $php_executable_finder->find();
     $this->root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
   }
 
@@ -40,14 +49,12 @@ protected function setUp() {
    * @coversNothing
    */
   public function testInstallWithNonExistingFile() {
-    $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 = $php_binary_path . ' core/scripts/test-site.php install --setup-file "this-class-does-not-exist" --db-url "' . getenv('SIMPLETEST_DB') . '"';
+    $command_line = $this->php . ' core/scripts/test-site.php install --setup-file "this-class-does-not-exist" --db-url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root);
     $process->run();
 
@@ -60,14 +67,12 @@ public function testInstallWithNonExistingFile() {
    * @coversNothing
    */
   public function testInstallWithFileWithNoClass() {
-    $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 = $php_binary_path . ' core/scripts/test-site.php install --setup-file core/tests/fixtures/empty_file.php.module --db-url "' . getenv('SIMPLETEST_DB') . '"';
+    $command_line = $this->php . ' core/scripts/test-site.php install --setup-file core/tests/fixtures/empty_file.php.module --db-url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root);
     $process->run();
 
@@ -80,15 +85,13 @@ public function testInstallWithFileWithNoClass() {
    * @coversNothing
    */
   public function testInstallWithNonSetupClass() {
-    $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('%'));
 
     // Use __FILE__ to test absolute paths.
-    $command_line = $php_binary_path . ' core/scripts/test-site.php install --setup-file "' . __FILE__ . '" --db-url "' . getenv('SIMPLETEST_DB') . '"';
+    $command_line = $this->php . ' core/scripts/test-site.php install --setup-file "' . __FILE__ . '" --db-url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root, ['COLUMNS' => PHP_INT_MAX]);
     $process->run();
 
@@ -106,11 +109,9 @@ public function testInstallScript() {
     if (!is_writable($simpletest_path)) {
       $this->markTestSkipped("Requires the directory $simpletest_path to exist and be writable");
     }
-    $php_binary_finder = new PhpExecutableFinder();
-    $php_binary_path = $php_binary_finder->find();
 
     // Install a site using the JSON output.
-    $command_line = $php_binary_path . ' core/scripts/test-site.php install --json --setup-file core/tests/Drupal/TestSite/TestSiteInstallTestScript.php --db-url "' . getenv('SIMPLETEST_DB') . '"';
+    $command_line = $this->php . ' core/scripts/test-site.php install --json --setup-file core/tests/Drupal/TestSite/TestSiteInstallTestScript.php --db-url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root);
     // Set the timeout to a value that allows debugging.
     $process->setTimeout(500);
@@ -142,7 +143,7 @@ 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') . '"';
+    $command_line = $this->php . ' 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);
     // Set the timeout to a value that allows debugging.
     $process->setTimeout(500);
@@ -160,7 +161,7 @@ public function testInstallScript() {
     $this->assertFileExists($this->getTestLockFile($other_db_prefix));
 
     // 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') . '"';
+    $command_line = $this->php . ' core/scripts/test-site.php tear-down ' . $db_prefix . ' --keep-lock --db-url "' . getenv('SIMPLETEST_DB') . '"';
     $process = new Process($command_line, $this->root);
     // Set the timeout to a value that allows debugging.
     $process->setTimeout(500);
@@ -182,7 +183,7 @@ public function testInstallScript() {
     // broken. Prove this by removing its settings.php.
     $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') . '"';
+    $command_line = $this->php . ' 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.
     $process->setTimeout(500);
@@ -208,10 +209,8 @@ public function testInstallInDifferentLanguage() {
     if (!is_writable($simpletest_path)) {
       $this->markTestSkipped("Requires the directory $simpletest_path to exist and be writable");
     }
-    $php_binary_finder = new PhpExecutableFinder();
-    $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') . '"';
+    $command_line = $this->php . ' 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);
     $process->setTimeout(500);
     $process->run();
@@ -229,7 +228,7 @@ public function testInstallInDifferentLanguage() {
     $this->assertContains('lang="fr"', (string) $response->getBody());
 
     // 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') . '"';
+    $command_line = $this->php . ' 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();
@@ -243,10 +242,7 @@ public function testInstallInDifferentLanguage() {
    * @coversNothing
    */
   public function testTearDownDbPrefixValidation() {
-    $php_binary_finder = new PhpExecutableFinder();
-    $php_binary_path = $php_binary_finder->find();
-
-    $command_line = $php_binary_path . ' core/scripts/test-site.php tear-down not-a-valid-prefix';
+    $command_line = $this->php . ' core/scripts/test-site.php tear-down not-a-valid-prefix';
     $process = new Process($command_line, $this->root);
     $process->setTimeout(500);
     $process->run();
@@ -254,6 +250,61 @@ public function testTearDownDbPrefixValidation() {
     $this->assertContains('Invalid database prefix: not-a-valid-prefix', $process->getErrorOutput());
   }
 
+  /**
+   * @coversNothing
+   */
+  public function testUserLogin() {
+    $simpletest_path = $this->root . DIRECTORY_SEPARATOR . 'sites' . DIRECTORY_SEPARATOR . 'simpletest';
+    if (!is_writable($simpletest_path)) {
+      $this->markTestSkipped("Requires the directory $simpletest_path to exist and be writable");
+    }
+
+    // Install a site using the JSON output.
+    $command_line = $this->php . ' core/scripts/test-site.php install --json --setup-file core/tests/Drupal/TestSite/TestSiteInstallTestScript.php --db-url "' . getenv('SIMPLETEST_DB') . '"';
+    $process = new Process($command_line, $this->root);
+    // Set the timeout to a value that allows debugging.
+    $process->setTimeout(500);
+    $process->run();
+
+    $this->assertSame(0, $process->getExitCode());
+    $result = json_decode($process->getOutput(), TRUE);
+    $db_prefix = $result['db_prefix'];
+    $site_path = $result['site_path'];
+    $this->assertSame('sites/simpletest/' . str_replace('test', '', $db_prefix), $site_path);
+
+    // Test the user login command with valid uid.
+    $command_line = $this->php . ' core/scripts/test-site.php user-login 1 --site-path ' . $site_path;
+    $process = new Process($command_line, $this->root);
+    $process->run();
+    $this->assertSame(0, $process->getExitCode());
+    $this->assertContains('/user/reset/1/', $process->getOutput());
+
+    $http_client = new Client();
+    $request = (new Request('GET', getenv('SIMPLETEST_BASE_URL') . trim($process->getOutput())))
+      ->withHeader('User-Agent', trim($result['user_agent']));
+
+    $response = $http_client->send($request);
+
+    // Ensure the response sets a new session.
+    $this->assertTrue($response->getHeader('Set-Cookie'));
+
+    // Test the user login command with invalid uid.
+    $command_line = $this->php . ' core/scripts/test-site.php user-login invalid-uid --site-path ' . $site_path;
+    $process = new Process($command_line, $this->root);
+    $process->run();
+    $this->assertSame(1, $process->getExitCode());
+    $this->assertContains('The "uid" argument needs to be an integer, but it is "invalid-uid".', $process->getErrorOutput());
+
+    // Now tear down the test site.
+    $command_line = $this->php . ' 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);
+    $process->run();
+    $this->assertSame(0, $process->getExitCode());
+    $this->assertContains("Successfully uninstalled $db_prefix test site", $process->getOutput());
+  }
+
   /**
    * Adds the installed test site to the database connection info.
    *