diff --git a/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php b/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php
index 9f004abba7..0bed72fbdc 100644
--- a/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php
@@ -88,7 +88,7 @@ public function testAnonymousNodeWithFile() {
       $this->assertNotEqual($nid, 0, 'The node ID was extracted from the URL.');
       $node = Node::load($nid);
       $this->assertNotEqual($node, NULL, 'The node was loaded successfully.');
-      $this->assertFileExists(File::load($node->field_image->target_id), 'The image was uploaded successfully.');
+      $this->assertFileExistsOnDisk(File::load($node->field_image->target_id), 'The image was uploaded successfully.');
     }
   }
 
@@ -162,7 +162,7 @@ protected function doTestNodeWithFileWithoutTitle() {
       $this->assertNotEqual($nid, 0, 'The node ID was extracted from the URL.');
       $node = Node::load($nid);
       $this->assertNotEqual($node, NULL, 'The node was loaded successfully.');
-      $this->assertFileExists(File::load($node->field_image->target_id), 'The image was uploaded successfully.');
+      $this->assertFileExistsOnDisk(File::load($node->field_image->target_id), 'The image was uploaded successfully.');
     }
   }
 
diff --git a/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php b/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php
index e4f7c80fd3..bb389dc0a6 100644
--- a/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php
@@ -39,7 +39,7 @@ public function testRevisions() {
     $node = $node_storage->load($nid);
     $node_file_r1 = File::load($node->{$field_name}->target_id);
     $node_vid_r1 = $node->getRevisionId();
-    $this->assertFileExists($node_file_r1, 'New file saved to disk on node creation.');
+    $this->assertFileExistsOnDisk($node_file_r1, 'New file saved to disk on node creation.');
     $this->assertFileEntryExists($node_file_r1, 'File entry exists in database on node creation.');
     $this->assertFileIsPermanent($node_file_r1, 'File is permanent.');
 
@@ -49,7 +49,7 @@ public function testRevisions() {
     $node = $node_storage->load($nid);
     $node_file_r2 = File::load($node->{$field_name}->target_id);
     $node_vid_r2 = $node->getRevisionId();
-    $this->assertFileExists($node_file_r2, 'Replacement file exists on disk after creating new revision.');
+    $this->assertFileExistsOnDisk($node_file_r2, 'Replacement file exists on disk after creating new revision.');
     $this->assertFileEntryExists($node_file_r2, 'Replacement file entry exists in database after creating new revision.');
     $this->assertFileIsPermanent($node_file_r2, 'Replacement file is permanent.');
 
@@ -57,7 +57,7 @@ public function testRevisions() {
     $node = node_revision_load($node_vid_r1);
     $current_file = File::load($node->{$field_name}->target_id);
     $this->assertEqual($node_file_r1->id(), $current_file->id(), 'Original file still in place after replacing file in new revision.');
-    $this->assertFileExists($node_file_r1, 'Original file still in place after replacing file in new revision.');
+    $this->assertFileExistsOnDisk($node_file_r1, 'Original file still in place after replacing file in new revision.');
     $this->assertFileEntryExists($node_file_r1, 'Original file entry still in place after replacing file in new revision');
     $this->assertFileIsPermanent($node_file_r1, 'Original file is still permanent.');
 
@@ -82,7 +82,7 @@ public function testRevisions() {
     // Delete the second revision and check that the file is kept (since it is
     // still being used by the third revision).
     $this->drupalPostForm('node/' . $nid . '/revisions/' . $node_vid_r2 . '/delete', [], t('Delete'));
-    $this->assertFileExists($node_file_r3, 'Second file is still available after deleting second revision, since it is being used by the third revision.');
+    $this->assertFileExistsOnDisk($node_file_r3, 'Second file is still available after deleting second revision, since it is being used by the third revision.');
     $this->assertFileEntryExists($node_file_r3, 'Second file entry is still available after deleting second revision, since it is being used by the third revision.');
     $this->assertFileIsPermanent($node_file_r3, 'Second file entry is still permanent after deleting second revision, since it is being used by the third revision.');
 
@@ -95,7 +95,7 @@ public function testRevisions() {
 
     // Delete the third revision and check that the file is not deleted yet.
     $this->drupalPostForm('node/' . $nid . '/revisions/' . $node_vid_r3 . '/delete', [], t('Delete'));
-    $this->assertFileExists($node_file_r3, 'Second file is still available after deleting third revision, since it is being used by the user.');
+    $this->assertFileExistsOnDisk($node_file_r3, 'Second file is still available after deleting third revision, since it is being used by the user.');
     $this->assertFileEntryExists($node_file_r3, 'Second file entry is still available after deleting third revision, since it is being used by the user.');
     $this->assertFileIsPermanent($node_file_r3, 'Second file entry is still permanent after deleting third revision, since it is being used by the user.');
 
@@ -120,7 +120,7 @@ public function testRevisions() {
       ->execute();
     \Drupal::service('cron')->run();
 
-    $this->assertFileNotExists($node_file_r3, 'Second file is now deleted after deleting third revision, since it is no longer being used by any other nodes.');
+    $this->assertFileNotExistsOnDisk($node_file_r3, 'Second file is now deleted after deleting third revision, since it is no longer being used by any other nodes.');
     $this->assertFileEntryNotExists($node_file_r3, 'Second file entry is now deleted after deleting third revision, since it is no longer being used by any other nodes.');
 
     // Delete the entire node and check that the original file is deleted.
@@ -135,7 +135,7 @@ public function testRevisions() {
       ->condition('fid', $node_file_r1->id())
       ->execute();
     \Drupal::service('cron')->run();
-    $this->assertFileNotExists($node_file_r1, 'Original file is deleted after deleting the entire node with two revisions remaining.');
+    $this->assertFileNotExistsOnDisk($node_file_r1, 'Original file is deleted after deleting the entire node with two revisions remaining.');
     $this->assertFileEntryNotExists($node_file_r1, 'Original file entry is deleted after deleting the entire node with two revisions remaining.');
   }
 
diff --git a/core/modules/file/tests/src/Functional/FileFieldTestBase.php b/core/modules/file/tests/src/Functional/FileFieldTestBase.php
index e946985323..e8f6569f74 100644
--- a/core/modules/file/tests/src/Functional/FileFieldTestBase.php
+++ b/core/modules/file/tests/src/Functional/FileFieldTestBase.php
@@ -264,7 +264,7 @@ public function replaceNodeFile($file, $field_name, $nid, $new_revision = TRUE)
   /**
    * Asserts that a file exists physically on disk.
    */
-  public function assertFileExists($file, $message = NULL) {
+  public function assertFileExistsOnDisk($file, $message = NULL) {
     $message = isset($message) ? $message : format_string('File %file exists on the disk.', ['%file' => $file->getFileUri()]);
     $this->assertTrue(is_file($file->getFileUri()), $message);
   }
@@ -282,7 +282,7 @@ public function assertFileEntryExists($file, $message = NULL) {
   /**
    * Asserts that a file does not exist on disk.
    */
-  public function assertFileNotExists($file, $message = NULL) {
+  public function assertFileNotExistsOnDisk($file, $message = NULL) {
     $message = isset($message) ? $message : format_string('File %file exists on the disk.', ['%file' => $file->getFileUri()]);
     $this->assertFalse(is_file($file->getFileUri()), $message);
   }
diff --git a/core/modules/file/tests/src/Functional/FileFieldValidateTest.php b/core/modules/file/tests/src/Functional/FileFieldValidateTest.php
index b2c5d4ecd7..546fed26e0 100644
--- a/core/modules/file/tests/src/Functional/FileFieldValidateTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldValidateTest.php
@@ -40,7 +40,7 @@ public function testRequired() {
     $node = $node_storage->load($nid);
 
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file, 'File exists after uploading to the required field.');
+    $this->assertFileExistsOnDisk($node_file, 'File exists after uploading to the required field.');
     $this->assertFileEntryExists($node_file, 'File entry exists after uploading to the required field.');
 
     // Try again with a multiple value field.
@@ -58,7 +58,7 @@ public function testRequired() {
     $node_storage->resetCache([$nid]);
     $node = $node_storage->load($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file, 'File exists after uploading to the required multiple value field.');
+    $this->assertFileExistsOnDisk($node_file, 'File exists after uploading to the required multiple value field.');
     $this->assertFileEntryExists($node_file, 'File entry exists after uploading to the required multiple value field.');
   }
 
@@ -90,7 +90,7 @@ public function testFileMaxSize() {
       $node_storage->resetCache([$nid]);
       $node = $node_storage->load($nid);
       $node_file = File::load($node->{$field_name}->target_id);
-      $this->assertFileExists($node_file, format_string('File exists after uploading a file (%filesize) under the max limit (%maxsize).', ['%filesize' => format_size($small_file->getSize()), '%maxsize' => $max_filesize]));
+      $this->assertFileExistsOnDisk($node_file, format_string('File exists after uploading a file (%filesize) under the max limit (%maxsize).', ['%filesize' => format_size($small_file->getSize()), '%maxsize' => $max_filesize]));
       $this->assertFileEntryExists($node_file, format_string('File entry exists after uploading a file (%filesize) under the max limit (%maxsize).', ['%filesize' => format_size($small_file->getSize()), '%maxsize' => $max_filesize]));
 
       // Check that uploading the large file fails (1M limit).
@@ -107,7 +107,7 @@ public function testFileMaxSize() {
     $node_storage->resetCache([$nid]);
     $node = $node_storage->load($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file, format_string('File exists after uploading a file (%filesize) with no max limit.', ['%filesize' => format_size($large_file->getSize())]));
+    $this->assertFileExistsOnDisk($node_file, format_string('File exists after uploading a file (%filesize) with no max limit.', ['%filesize' => format_size($large_file->getSize())]));
     $this->assertFileEntryExists($node_file, format_string('File entry exists after uploading a file (%filesize) with no max limit.', ['%filesize' => format_size($large_file->getSize())]));
   }
 
@@ -131,7 +131,7 @@ public function testFileExtension() {
     $node_storage->resetCache([$nid]);
     $node = $node_storage->load($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file, 'File exists after uploading a file with no extension checking.');
+    $this->assertFileExistsOnDisk($node_file, 'File exists after uploading a file with no extension checking.');
     $this->assertFileEntryExists($node_file, 'File entry exists after uploading a file with no extension checking.');
 
     // Enable extension checking for text files.
@@ -150,7 +150,7 @@ public function testFileExtension() {
     $node_storage->resetCache([$nid]);
     $node = $node_storage->load($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file, 'File exists after uploading a file with extension checking.');
+    $this->assertFileExistsOnDisk($node_file, 'File exists after uploading a file with extension checking.');
     $this->assertFileEntryExists($node_file, 'File entry exists after uploading a file with extension checking.');
   }
 
@@ -173,7 +173,7 @@ public function testFileRemoval() {
     $node_storage->resetCache([$nid]);
     $node = $node_storage->load($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file, 'File exists after uploading a file with no extension checking.');
+    $this->assertFileExistsOnDisk($node_file, 'File exists after uploading a file with no extension checking.');
     $this->assertFileEntryExists($node_file, 'File entry exists after uploading a file with no extension checking.');
 
     // Enable extension checking for text files.
diff --git a/core/modules/file/tests/src/Functional/FileFieldWidgetTest.php b/core/modules/file/tests/src/Functional/FileFieldWidgetTest.php
index 97d7eb6d6d..c6cec35814 100644
--- a/core/modules/file/tests/src/Functional/FileFieldWidgetTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldWidgetTest.php
@@ -90,7 +90,7 @@ public function testSingleValuedWidget() {
       $node_storage->resetCache([$nid]);
       $node = $node_storage->load($nid);
       $node_file = File::load($node->{$field_name}->target_id);
-      $this->assertFileExists($node_file, 'New file saved to disk on node creation.');
+      $this->assertFileExistsOnDisk($node_file, 'New file saved to disk on node creation.');
 
       // Ensure the file can be downloaded.
       $this->drupalGet(file_create_url($node_file->getFileUri()));
@@ -320,7 +320,7 @@ public function testPrivateFileSetting() {
     $node_storage->resetCache([$nid]);
     $node = $node_storage->load($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file, 'New file saved to disk on node creation.');
+    $this->assertFileExistsOnDisk($node_file, 'New file saved to disk on node creation.');
 
     // Ensure the private file is available to the user who uploaded it.
     $this->drupalGet(file_create_url($node_file->getFileUri()));
@@ -387,7 +387,7 @@ public function testPrivateFileComment() {
 
     $comment = Comment::load($cid);
     $comment_file = $comment->{'field_' . $name}->entity;
-    $this->assertFileExists($comment_file, 'New file saved to disk on node creation.');
+    $this->assertFileExistsOnDisk($comment_file, 'New file saved to disk on node creation.');
     // Test authenticated file download.
     $url = file_create_url($comment_file->getFileUri());
     $this->assertNotEqual($url, NULL, 'Confirmed that the URL is valid');
@@ -572,7 +572,7 @@ protected function doTestTemporaryFileRemovalExploit(UserInterface $victim_user,
 
       /** @var \Drupal\file\FileInterface $node_file */
       $node_file = File::load($node->{$field_name}->target_id);
-      $this->assertFileExists($node_file, 'A file was saved to disk on node creation');
+      $this->assertFileExistsOnDisk($node_file, 'A file was saved to disk on node creation');
       $this->assertEqual($attacker_user->id(), $node_file->getOwnerId(), 'New file belongs to the attacker.');
 
       // Ensure the file can be downloaded.
@@ -595,7 +595,7 @@ protected function doTestTemporaryFileRemovalExploit(UserInterface $victim_user,
 
       // The victim's temporary file should not be removed by the attacker's
       // POST request.
-      $this->assertFileExists($victim_tmp_file);
+      $this->assertFileExistsOnDisk($victim_tmp_file);
     }
   }
 
diff --git a/core/modules/file/tests/src/Functional/SaveUploadTest.php b/core/modules/file/tests/src/Functional/SaveUploadTest.php
index b6405b5bf1..9382c8b4a6 100644
--- a/core/modules/file/tests/src/Functional/SaveUploadTest.php
+++ b/core/modules/file/tests/src/Functional/SaveUploadTest.php
@@ -3,6 +3,7 @@
 namespace Drupal\Tests\file\Functional;
 
 use Drupal\file\Entity\File;
+use Drupal\Tests\TestFileCreationTrait;
 
 /**
  * Tests the file_save_upload() function.
@@ -10,6 +11,11 @@
  * @group file
  */
 class SaveUploadTest extends FileManagedTestBase {
+
+  use TestFileCreationTrait {
+    getTestFiles as drupalGetTestFiles;
+  }
+
   /**
    * Modules to enable.
    *