diff --git a/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php b/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php
index f2e1386..ed29ebe 100644
--- a/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php
+++ b/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php
@@ -313,6 +313,21 @@ public function configureTitle($foo) {
   }
 
   /**
+   * Simple argument echo.
+   *
+   * @param string $text
+   *   Any string for the {text} slug.
+   *
+   * @return array
+   *   A render array.
+   */
+  public function simpleEcho($text) {
+    return [
+      '#plain_text' => $text,
+    ];
+  }
+
+  /**
    * Shows permission-dependent content.
    *
    * @return array
diff --git a/core/modules/system/tests/modules/system_test/system_test.routing.yml b/core/modules/system/tests/modules/system_test/system_test.routing.yml
index f35f546..eac36c6 100644
--- a/core/modules/system/tests/modules/system_test/system_test.routing.yml
+++ b/core/modules/system/tests/modules/system_test/system_test.routing.yml
@@ -182,3 +182,10 @@ system_test.header:
     _controller: '\Drupal\system_test\Controller\SystemTestController::getTestHeader'
   requirements:
     _access: 'TRUE'
+
+system_test.echo:
+  path: '/system-test/echo/{text}'
+  defaults:
+    _controller: '\Drupal\system_test\Controller\SystemTestController::simpleEcho'
+  requirements:
+    _access: 'TRUE'
diff --git a/core/tests/Drupal/FunctionalTests/Routing/CaseInsensitivePathTest.php b/core/tests/Drupal/FunctionalTests/Routing/CaseInsensitivePathTest.php
index 83c58b5..906ffef 100644
--- a/core/tests/Drupal/FunctionalTests/Routing/CaseInsensitivePathTest.php
+++ b/core/tests/Drupal/FunctionalTests/Routing/CaseInsensitivePathTest.php
@@ -5,7 +5,7 @@
 use Drupal\Tests\BrowserTestBase;
 
 /**
- * Tests url generation and routing for route paths with encoded characters.
+ * Tests incoming path case insensitivity.
  *
  * @group routing
  */
@@ -14,8 +14,19 @@ class CaseInsensitivePathTest extends BrowserTestBase {
   /**
    * {@inheritdoc}
    */
-  public static $modules = ['system', 'views', 'node'];
+  public static $modules = ['system', 'views', 'node', 'system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    \Drupal::state()->set('system_test.module_hidden', FALSE);
+  }
+
+  /**
+   * Tests paths defined by routes from standard modules.
+   */
   public function testInternalPath() {
     $this->drupalGet('user/login');
     $this->assertEquals($this->getSession()->getStatusCode(), 200);
@@ -23,14 +34,70 @@ public function testInternalPath() {
     $this->assertEquals($this->getSession()->getStatusCode(), 200);
   }
 
+  /**
+   * Tests paths defined by routes from the Views module.
+   */
   public function testViewsPath() {
     $admin = $this->drupalCreateUser(['access administration pages', 'administer nodes', 'access content overview']);
     $this->drupalLogin($admin);
 
     $this->drupalGet('admin/content');
-    $this->assertEquals($this->getSession()->getStatusCode(), 200);
+    $this->assertEquals(200, $this->getSession()->getStatusCode());
     $this->drupalGet('Admin/Content');
-    $this->assertEquals($this->getSession()->getStatusCode(), 200);
+    $this->assertEquals(200, $this->getSession()->getStatusCode());
+  }
+
+  /**
+   * Tests paths with query arguments.
+   */
+  public function testPathsWithQuery() {
+    $admin = $this->drupalCreateUser(['access administration pages', 'administer nodes', 'access content overview']);
+    $this->drupalLogin($admin);
+
+    // Make sure our node title doesn't exist.
+    $this->drupalGet('admin/content');
+    $this->assertSession()->linkNotExists('FooBarBaz');
+    $this->assertSession()->linkNotExists('foobarbaz');
+
+    // Create a node, and make sure it shows up on admin/content.
+    $node = $this->createNode([
+      'title' => 'FooBarBaz',
+      'type' => 'page',
+    ]);
+
+    $this->drupalGet('admin/content', [
+      'query' => [
+        'title' => 'FooBarBaz'
+      ]
+    ]);
+
+    $this->assertSession()->linkExists('FooBarBaz');
+    $this->assertSession()->linkByHrefExists($node->toUrl()->toString());
+
+    // Make sure the path is case insensitive, and query case is preserved.
+
+    $this->drupalGet('Admin/Content', [
+      'query' => [
+        'title' => 'FooBarBaz'
+      ]
+    ]);
+
+    $this->assertSession()->linkExists('FooBarBaz');
+    $this->assertSession()->linkByHrefExists($node->toUrl()->toString());
+    $this->assertSession()->fieldValueEquals('edit-title', 'FooBarBaz');
+  }
+
+  /**
+   * Tests paths with slugs.
+   */
+  public function testPathsWithArguments() {
+    $this->drupalGet('system-test/echo/foobarbaz');
+    $this->assertSession()->responseMatches('/foobarbaz/');
+    $this->assertSession()->responseNotMatches('/FooBarBaz/');
+
+    $this->drupalGet('system-test/echo/FooBarBaz');
+    $this->assertSession()->responseMatches('/FooBarBaz/');
+    $this->assertSession()->responseNotMatches('/foobarbaz/');
   }
 
 }