diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index cb454a1..8db7ac3 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -38,6 +38,7 @@
 abstract class WebTestBase extends TestBase {
 
   use AssertContentTrait;
+  use TestFileCreationTrait;
   use BlockCreationTrait {
     placeBlock as drupalPlaceBlock;
   }
@@ -332,99 +333,6 @@ protected function findBlockInstance(Block $block) {
   }
 
   /**
-   * Gets a list of files that can be used in tests.
-   *
-   * The first time this method is called, it will call
-   * simpletest_generate_file() to generate binary and ASCII text files in the
-   * public:// directory. It will also copy all files in
-   * core/modules/simpletest/files to public://. These contain image, SQL, PHP,
-   * JavaScript, and HTML files.
-   *
-   * All filenames are prefixed with their type and have appropriate extensions:
-   * - text-*.txt
-   * - binary-*.txt
-   * - html-*.html and html-*.txt
-   * - image-*.png, image-*.jpg, and image-*.gif
-   * - javascript-*.txt and javascript-*.script
-   * - php-*.txt and php-*.php
-   * - sql-*.txt and sql-*.sql
-   *
-   * Any subsequent calls will not generate any new files, or copy the files
-   * over again. However, if a test class adds a new file to public:// that
-   * is prefixed with one of the above types, it will get returned as well, even
-   * on subsequent calls.
-   *
-   * @param $type
-   *   File type, possible values: 'binary', 'html', 'image', 'javascript',
-   *   'php', 'sql', 'text'.
-   * @param $size
-   *   (optional) File size in bytes to match. Defaults to NULL, which will not
-   *   filter the returned list by size.
-   *
-   * @return
-   *   List of files in public:// that match the filter(s).
-   */
-  protected function drupalGetTestFiles($type, $size = NULL) {
-    if (empty($this->generatedTestFiles)) {
-      // Generate binary test files.
-      $lines = array(64, 1024);
-      $count = 0;
-      foreach ($lines as $line) {
-        simpletest_generate_file('binary-' . $count++, 64, $line, 'binary');
-      }
-
-      // Generate ASCII text test files.
-      $lines = array(16, 256, 1024, 2048, 20480);
-      $count = 0;
-      foreach ($lines as $line) {
-        simpletest_generate_file('text-' . $count++, 64, $line, 'text');
-      }
-
-      // Copy other test files from simpletest.
-      $original = drupal_get_path('module', 'simpletest') . '/files';
-      $files = file_scan_directory($original, '/(html|image|javascript|php|sql)-.*/');
-      foreach ($files as $file) {
-        file_unmanaged_copy($file->uri, PublicStream::basePath());
-      }
-
-      $this->generatedTestFiles = TRUE;
-    }
-
-    $files = array();
-    // Make sure type is valid.
-    if (in_array($type, array('binary', 'html', 'image', 'javascript', 'php', 'sql', 'text'))) {
-      $files = file_scan_directory('public://', '/' . $type . '\-.*/');
-
-      // If size is set then remove any files that are not of that size.
-      if ($size !== NULL) {
-        foreach ($files as $file) {
-          $stats = stat($file->uri);
-          if ($stats['size'] != $size) {
-            unset($files[$file->uri]);
-          }
-        }
-      }
-    }
-    usort($files, array($this, 'drupalCompareFiles'));
-    return $files;
-  }
-
-  /**
-   * Compare two files based on size and file name.
-   */
-  protected function drupalCompareFiles($file1, $file2) {
-    $compare_size = filesize($file1->uri) - filesize($file2->uri);
-    if ($compare_size) {
-      // Sort by file size.
-      return $compare_size;
-    }
-    else {
-      // The files were the same size, so sort alphabetically.
-      return strnatcmp($file1->name, $file2->name);
-    }
-  }
-
-  /**
    * Log in a user with the internal browser.
    *
    * If a user is already logged in, then the current user is logged out before