diff --git a/core/modules/basic_auth/src/Tests/BasicAuthTestTrait.php b/core/modules/basic_auth/src/Tests/BasicAuthTestTrait.php
index ae27db5..2d04672 100644
--- a/core/modules/basic_auth/src/Tests/BasicAuthTestTrait.php
+++ b/core/modules/basic_auth/src/Tests/BasicAuthTestTrait.php
@@ -32,10 +32,7 @@ protected function basicAuthGet($path, $username, $password, array $options = []
   }
 
   /**
-   * Executes a form submission.
-   *
-   * This uses the same format as WebTestBase::drupalPostForm(), but uses basic
-   * authentication.
+   * Executes a form submission using basic authentication.
    *
    * @param string $path
    *   Location of the post form.
diff --git a/core/modules/system/src/Tests/Session/SessionAuthenticationTest.php b/core/modules/system/src/Tests/Session/SessionAuthenticationTest.php
index 493d7d2..1a67266 100644
--- a/core/modules/system/src/Tests/Session/SessionAuthenticationTest.php
+++ b/core/modules/system/src/Tests/Session/SessionAuthenticationTest.php
@@ -28,20 +28,6 @@ class SessionAuthenticationTest extends WebTestBase {
   protected $user;
 
   /**
-   * The username of the test user.
-   *
-   * @var string
-   */
-  protected $username;
-
-  /**
-   * The password of the test user.
-   *
-   * @var string
-   */
-  protected $password;
-
-  /**
    * {@inheritdoc}
    */
   public static $modules = ['basic_auth', 'session_test'];
@@ -54,8 +40,6 @@ protected function setUp() {
 
     // Create a test administrator user.
     $this->user = $this->drupalCreateUser(['administer site configuration']);
-    $this->username = $this->user->getUsername();
-    $this->password = $this->user->pass_raw;
   }
 
   /**
@@ -76,7 +60,7 @@ public function testSessionFromBasicAuthenticationDoesNotLeak() {
     $this->assertResponse(401, 'An anonymous user cannot access a route protected with basic authentication.');
 
     // We should be able to access the route with basic authentication.
-    $this->basicAuthGet($protected_url, $this->username, $this->password);
+    $this->basicAuthGet($protected_url, $this->user->getUsername(), $this->user->pass_raw);
     $this->assertResponse(200, 'A route protected with basic authentication can be accessed by an authenticated user.');
 
     // Check that the correct user is logged in.
@@ -95,43 +79,35 @@ public function testSessionFromBasicAuthenticationDoesNotLeak() {
   }
 
   /**
-   * Tests logging in using basic authentication.
-   */
-  public function testLoginWithBasicAuthCredentials() {
-    // If we use basic authentication with valid credentials this results in a
-    // successful authentication. When we are already authenticated we should
-    // be denied access when submitting the login form.
-    $edit = ['name' => $this->username, 'pass' => $this->password];
-
-    $this->basicAuthPostForm('<front>', $edit, t('Log in'), $this->username, $this->password);
-    $this->assertResponse(403);
-
-    // Basic auth doesn't set a cookie, so if we do a subsequent request without
-    // using basic authentication we are no longer logged in.
-    $this->drupalGet($this->user->urlInfo());
-    $this->assertResponse(403);
-
-    // Let's send some basic_auth authentication headers, but that particular
-    // route does not have basic_auth authentications.
-    $this->basicAuthGet($this->user->urlInfo(), $this->username, $this->password);
-    $this->assertResponse(403);
-  }
-
-  /**
    * Tests if a session can be initiated through basic authentication.
    */
   public function testBasicAuthSession() {
     // Set a session value on a request through basic auth.
-    $test_session_value = 'alpaca';
-    $this->basicAuthGet('session-test/set-session/' . $test_session_value, $this->user->getUsername(), $this->user->pass_raw);
+    $test_value = 'alpaca';
+    $response = $this->basicAuthGet('session-test/set-session/' . $test_value, $this->user->getUsername(), $this->user->pass_raw);
+    $this->assertSessionData($response, $test_value);
+    $this->assertResponse(200, 'The request to set a session value was successful.');
 
     // Test that on a subsequent request the session value is still present.
-    $result = $this->basicAuthGet('session-test/get-session', $this->username, $this->password);
-    $data = json_decode($result, TRUE);
-    $this->assertEqual(['test_value' => $test_session_value], $data['session']);
+    $response = $this->basicAuthGet('session-test/get-session', $this->user->getUsername(), $this->user->pass_raw);
+    $this->assertSessionData($response, $test_value);
+    $this->assertResponse(200, 'The request to get a session value was successful.');
+  }
+
+  /**
+   * Checks the session data returned by the session test routes.
+   *
+   * @param string $response
+   *   A response object containing the session values and the user ID.
+   * @param string $expected
+   *   The expected session value.
+   */
+  protected function assertSessionData($response, $expected) {
+    $response = json_decode($response, TRUE);
+    $this->assertEqual(['test_value' => $expected], $response['session'], 'The session data matches the expected value.');
 
-    // Check that we are still logged in as the same user.
-    $this->assertEqual($this->user->id(), $data['user']);
+    // Check that we are logged in as the correct user.
+    $this->assertEqual($this->user->id(), $response['user'], 'The correct user is logged in.');
   }
 
 }
diff --git a/core/modules/system/tests/modules/session_test/src/Controller/SessionTestController.php b/core/modules/system/tests/modules/session_test/src/Controller/SessionTestController.php
index b5333ee..b17d9a0 100644
--- a/core/modules/system/tests/modules/session_test/src/Controller/SessionTestController.php
+++ b/core/modules/system/tests/modules/session_test/src/Controller/SessionTestController.php
@@ -189,8 +189,7 @@ public function getSession(Request $request) {
   public function setSession(Request $request, $test_value) {
     $session = $request->getSession();
     $session->set('test_value', $test_value);
-    // Nothing to see here, just return 200 OK.
-    return new Response();
+    return new JsonResponse(['session' => $session->all(), 'user' => $this->currentUser()->id()]);
   }
 
 }