diff -u b/core/modules/page_cache/tests/src/Functional/PageCacheTest.php b/core/modules/page_cache/tests/src/Functional/PageCacheTest.php
--- b/core/modules/page_cache/tests/src/Functional/PageCacheTest.php
+++ b/core/modules/page_cache/tests/src/Functional/PageCacheTest.php
@@ -7,8 +7,8 @@
 use Drupal\Core\Url;
 use Drupal\entity_test\Entity\EntityTest;
 use Drupal\Core\Cache\Cache;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\user\RoleInterface;
 
 /**
@@ -191,7 +191,7 @@
     // Verify the page is not printed twice when the cache is cold.
     $this->assertNoPattern('#<html.*<html#');
 
-    $this->drupalHead('');
+    $this->drupalGet('');
     $this->assertEqual($this->drupalGetHeader('X-Drupal-Cache'), 'HIT', 'Page was cached.');
     $etag = $this->drupalGetHeader('ETag');
     $last_modified = $this->drupalGetHeader('Last-Modified');
@@ -199,10 +199,16 @@
     $this->drupalGet('', [], ['If-Modified-Since' => $last_modified, 'If-None-Match' => $etag]);
     $this->assertResponse(304, 'Conditional request returned 304 Not Modified.');
 
-    $this->drupalGet('', [], ['If-Modified-Since' => gmdate(DATE_RFC822, strtotime($last_modified)), 'If-None-Match' => $etag]);
+    $this->drupalGet('', [], [
+      'If-Modified-Since' => gmdate(DATE_RFC822, strtotime($last_modified)),
+      'If-None-Match' => $etag,
+    ]);
     $this->assertResponse(304, 'Conditional request with obsolete If-Modified-Since date returned 304 Not Modified.');
 
-    $this->drupalGet('', [], ['If-Modified-Since' => gmdate(DATE_RFC850, strtotime($last_modified)), 'If-None-Match' => $etag]);
+    $this->drupalGet('', [], [
+      'If-Modified-Since' => gmdate(DATE_RFC850, strtotime($last_modified)),
+      'If-None-Match' => $etag,
+    ]);
     $this->assertResponse(304, 'Conditional request with obsolete If-Modified-Since date returned 304 Not Modified.');
 
     $this->drupalGet('', [], ['If-Modified-Since' => $last_modified, 'If-None-Match' => NULL]);
@@ -211,7 +217,10 @@
     $this->assertResponse(200, 'Conditional request without If-None-Match returned 200 OK.');
     $this->assertEqual($this->drupalGetHeader('X-Drupal-Cache'), 'HIT', 'Page was cached.');
 
-    $this->drupalGet('', [], ['If-Modified-Since' => gmdate(DateTimePlus::RFC7231, strtotime($last_modified) + 1), 'If-None-Match' => $etag]);
+    $this->drupalGet('', [], [
+      'If-Modified-Since' => gmdate(DateTimePlus::RFC7231, strtotime($last_modified) + 1),
+      'If-None-Match' => $etag,
+    ]);
     $this->assertResponse(200, 'Conditional request with new a If-Modified-Since date newer than Last-Modified returned 200 OK.');
     $this->assertEqual($this->drupalGetHeader('X-Drupal-Cache'), 'HIT', 'Page was cached.');
 
@@ -521,29 +530,30 @@
    * Tests that HEAD requests are treated the same as GET requests.
    */
   public function testHead() {
-    /** @var \GuzzleHttp\Client $client */
+    /** @var \GuzzleHttp\ClientInterface $client */
     $client = $this->getSession()->getDriver()->getClient()->getClient();
+
     // GET, then HEAD.
     $url_a = $this->buildUrl('system-test/set-header', ['query' => ['name' => 'Foo', 'value' => 'bar']]);
-    $response = $this->drupalGet($url_a);
+    $response_body = $this->drupalGet($url_a);
     $this->assertEqual($this->drupalGetHeader('X-Drupal-Cache'), 'MISS', 'Page was not cached.');
     $this->assertEqual($this->drupalGetHeader('Foo'), 'bar', 'Custom header was sent.');
-    $this->assertEqual('The following header was set: <em class="placeholder">Foo</em>: <em class="placeholder">bar</em>', $response);
+    $this->assertEqual('The following header was set: <em class="placeholder">Foo</em>: <em class="placeholder">bar</em>', $response_body);
     $response = $client->request('HEAD', $url_a);
-    $this->assertEquals(['HIT'], $response->getHeader('X-Drupal-Cache'), 'Page was cached.');
-    $this->assertEquals(['bar'], $response->getHeader('Foo'), 'Custom header was sent.');
-    $this->assertEqual('', (string) $response->getBody());
+    $this->assertEqual($response->getHeaderLine('X-Drupal-Cache'), 'HIT', 'Page was cached.');
+    $this->assertEqual($response->getHeaderLine('Foo'), 'bar', 'Custom header was sent.');
+    $this->assertEqual('', $response->getBody()->getContents());
 
     // HEAD, then GET.
     $url_b = $this->buildUrl('system-test/set-header', ['query' => ['name' => 'Foo', 'value' => 'baz']]);
     $response = $client->request('HEAD', $url_b);
-    $this->assertEquals(['MISS'], $response->getHeader('X-Drupal-Cache'), 'Page was not cached.');
-    $this->assertEquals(['baz'], $response->getHeader('Foo'), 'Custom header was sent.');
-    $this->assertEqual('', (string) $response->getBody());
-    $response = $this->drupalGet($url_b);
+    $this->assertEqual($response->getHeaderLine('X-Drupal-Cache'), 'MISS', 'Page was not cached.');
+    $this->assertEqual($response->getHeaderLine('Foo'), 'baz', 'Custom header was sent.');
+    $this->assertEqual('', $response->getBody()->getContents());
+    $response_body = $this->drupalGet($url_b);
     $this->assertEqual($this->drupalGetHeader('X-Drupal-Cache'), 'HIT', 'Page was cached.');
     $this->assertEqual($this->drupalGetHeader('Foo'), 'baz', 'Custom header was sent.');
-    $this->assertEqual('The following header was set: <em class="placeholder">Foo</em>: <em class="placeholder">baz</em>', $response);
+    $this->assertEqual('The following header was set: <em class="placeholder">Foo</em>: <em class="placeholder">baz</em>', $response_body);
   }
 
   /**
@@ -563,8 +573,4 @@
       ],
       [
-        $url . '?',
-        $url . '',
-      ],
-      [
         $url . '?a=b+c',
         $url . '?a=b%20c',
reverted:
--- b/core/tests/Drupal/Tests/BrowserTestBase.php
+++ a/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -1419,44 +1419,4 @@
     return FALSE;
   }
 
-  /**
-   * Retrieves only the headers for a Drupal path or an absolute path.
-   *
-   * @param \Drupal\Core\Url|string $path
-   *   Drupal path or URL to load into internal browser.
-   * @param array $options
-   *   Options to be forwarded to the url generator.
-   * @param array $headers
-   *   An array containing additional HTTP request headers, each formatted as
-   *   "name: value".
-   *
-   * @return array
-   *   The retrieved headers, also available as $this->getRawContent()
-   */
-  protected function drupalHead($path, array $options = [], array $headers = []) {
-    $options['absolute'] = TRUE;
-    $url = $this->buildUrl($path, $options);
-    $session = $this->getSession();
-    $this->prepareRequest();
-    foreach ($headers as $header_name => $header_value) {
-      $session->setRequestHeader($header_name, $header_value);
-    }
-    $session->visit($url);
-    $out = $session->getResponseHeaders();
-
-    // Ensure that any changes to variables in the other thread are picked up.
-    $this->refreshVariables();
-
-    // Log only for JavascriptTestBase tests because for Goutte we log with
-    // ::getResponseLogHandler.
-    if ($this->htmlOutputEnabled && !($this->getSession()->getDriver() instanceof GoutteDriver)) {
-      $html_output = 'GET request to: ' . $url .
-        '<hr />Ending URL: ' . $this->getSession()->getCurrentUrl();
-      $html_output .= '<hr />' . $out;
-      $html_output .= $this->getHtmlOutputHeaders();
-      $this->htmlOutput($html_output);
-    }
-    return $out;
-  }
-
 }