diff --git a/core/modules/simpletest/src/TestFileCreationTrait.php b/core/modules/simpletest/src/TestFileCreationTrait.php
new file mode 100644
index 0000000..8def350
--- /dev/null
+++ b/core/modules/simpletest/src/TestFileCreationTrait.php
@@ -0,0 +1,108 @@
+<?php
+
+namespace Drupal\simpletest;
+
+use Drupal\Core\StreamWrapper\PublicStream;
+
+/**
+ * Provides methods to create content type from given values.
+ *
+ * This trait is meant to be used only by test classes.
+ */
+trait TestFileCreationTrait {
+
+  /**
+   * 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);
+    }
+  }
+
+
+}