diff --git a/modules/simpletest/drupal_web_test_case.php b/modules/simpletest/drupal_web_test_case.php
index d7350698c98e925247394d485130f6edeb6e8e1d..bf1e9c31c77415a5b36ac8eee426195d09141257 100644
--- a/modules/simpletest/drupal_web_test_case.php
+++ b/modules/simpletest/drupal_web_test_case.php
@@ -1065,7 +1065,7 @@ protected function drupalGetTestFiles($type, $size = NULL) {
       $lines = array(16, 256, 1024, 2048, 20480);
       $count = 0;
       foreach ($lines as $line) {
-        simpletest_generate_file('text-' . $count++, 64, $line);
+        simpletest_generate_file('text-' . $count++, 64, $line, 'text');
       }
 
       // Copy other test files from simpletest.
diff --git a/modules/simpletest/simpletest.module b/modules/simpletest/simpletest.module
index 91f0f9065e854fb4e4bd142e197575b4848fe643..a98e5cfbe1952426b74b6e9fcc1e88d04922cb25 100644
--- a/modules/simpletest/simpletest.module
+++ b/modules/simpletest/simpletest.module
@@ -509,25 +509,25 @@ function simpletest_registry_files_alter(&$files, $modules) {
  * Generate test file.
  */
 function simpletest_generate_file($filename, $width, $lines, $type = 'binary-text') {
-  $size = $width * $lines - $lines;
-
-  // Generate random text
   $text = '';
-  for ($i = 0; $i < $size; $i++) {
-    switch ($type) {
-      case 'text':
-        $text .= chr(rand(32, 126));
-        break;
-      case 'binary':
-        $text .= chr(rand(0, 31));
-        break;
-      case 'binary-text':
-      default:
-        $text .= rand(0, 1);
-        break;
+  for ($i = 0; $i < $lines; $i++) {
+    // Generate $width - 1 characters to leave space for the "\n" character.
+    for ($j = 0; $j < $width - 1; $j++) {
+      switch ($type) {
+        case 'text':
+          $text .= chr(rand(32, 126));
+          break;
+        case 'binary':
+          $text .= chr(rand(0, 31));
+          break;
+        case 'binary-text':
+        default:
+          $text .= rand(0, 1);
+          break;
+      }
     }
+    $text .= "\n";
   }
-  $text = wordwrap($text, $width - 1, "\n", TRUE) . "\n"; // Add \n for symmetrical file.
 
   // Create filename.
   file_put_contents('public://' . $filename . '.txt', $text);