diff --git a/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php b/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php
index 0cee386a287..48937fe4ee4 100644
--- a/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php
@@ -93,7 +93,7 @@ class FileFieldAnonymousSubmissionTest extends FileFieldTestBase {
       $this->assertNotEqual($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)->getFileUri(), 'The image was uploaded successfully.');
+      $this->assertFileExists(File::load($node->field_image->target_id)->getFileUri());
     }
   }
 
@@ -167,7 +167,7 @@ class FileFieldAnonymousSubmissionTest extends FileFieldTestBase {
       $this->assertNotEqual($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)->getFileUri(), 'The image was uploaded successfully.');
+      $this->assertFileExists(File::load($node->field_image->target_id)->getFileUri());
     }
   }
 
diff --git a/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php b/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php
index 39136b2f55e..e812cd8ee4c 100644
--- a/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php
@@ -51,7 +51,7 @@ class FileFieldRevisionTest extends FileFieldTestBase {
     $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->getFileUri(), 'New file saved to disk on node creation.');
+    $this->assertFileExists($node_file_r1->getFileUri());
     $this->assertFileEntryExists($node_file_r1, 'File entry exists in database on node creation.');
     $this->assertFileIsPermanent($node_file_r1, 'File is permanent.');
 
@@ -61,7 +61,7 @@ class FileFieldRevisionTest extends FileFieldTestBase {
     $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->getFileUri(), 'Replacement file exists on disk after creating new revision.');
+    $this->assertFileExists($node_file_r2->getFileUri());
     $this->assertFileEntryExists($node_file_r2, 'Replacement file entry exists in database after creating new revision.');
     $this->assertFileIsPermanent($node_file_r2, 'Replacement file is permanent.');
 
@@ -69,7 +69,7 @@ class FileFieldRevisionTest extends FileFieldTestBase {
     $node = node_revision_load($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->getFileUri(), 'Original file still in place after replacing file in new revision.');
+    $this->assertFileExists($node_file_r1->getFileUri());
     $this->assertFileEntryExists($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.');
 
@@ -94,7 +94,7 @@ class FileFieldRevisionTest extends FileFieldTestBase {
     // 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->getFileUri(), 'Second file is still available after deleting second revision, since it is being used by the third revision.');
+    $this->assertFileExists($node_file_r3->getFileUri());
     $this->assertFileEntryExists($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.');
 
@@ -107,7 +107,7 @@ class FileFieldRevisionTest extends FileFieldTestBase {
 
     // 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->getFileUri(), 'Second file is still available after deleting third revision, since it is being used by the user.');
+    $this->assertFileExists($node_file_r3->getFileUri());
     $this->assertFileEntryExists($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.');
 
@@ -134,7 +134,7 @@ class FileFieldRevisionTest extends FileFieldTestBase {
       ->execute();
     \Drupal::service('cron')->run();
 
-    $this->assertFileNotExists($node_file_r3->getFileUri(), 'Second file is now deleted after deleting third revision, since it is no longer being used by any other nodes.');
+    $this->assertFileNotExists($node_file_r3->getFileUri());
     $this->assertFileEntryNotExists($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.
@@ -150,7 +150,7 @@ class FileFieldRevisionTest extends FileFieldTestBase {
       ->condition('fid', $node_file_r1->id())
       ->execute();
     \Drupal::service('cron')->run();
-    $this->assertFileNotExists($node_file_r1->getFileUri(), 'Original file is deleted after deleting the entire node with two revisions remaining.');
+    $this->assertFileNotExists($node_file_r1->getFileUri());
     $this->assertFileEntryNotExists($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/FileFieldValidateTest.php b/core/modules/file/tests/src/Functional/FileFieldValidateTest.php
index 334cdf47c03..51698a6257f 100644
--- a/core/modules/file/tests/src/Functional/FileFieldValidateTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldValidateTest.php
@@ -46,7 +46,7 @@ class FileFieldValidateTest extends FileFieldTestBase {
     $node = $node_storage->load($nid);
 
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file->getFileUri(), 'File exists after uploading to the required field.');
+    $this->assertFileExists($node_file->getFileUri());
     $this->assertFileEntryExists($node_file, 'File entry exists after uploading to the required field.');
 
     // Try again with a multiple value field.
@@ -64,7 +64,7 @@ class FileFieldValidateTest extends FileFieldTestBase {
     $node_storage->resetCache([$nid]);
     $node = $node_storage->load($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file->getFileUri(), 'File exists after uploading to the required multiple value field.');
+    $this->assertFileExists($node_file->getFileUri());
     $this->assertFileEntryExists($node_file, 'File entry exists after uploading to the required multiple value field.');
   }
 
@@ -98,7 +98,7 @@ class FileFieldValidateTest extends FileFieldTestBase {
       $node_storage->resetCache([$nid]);
       $node = $node_storage->load($nid);
       $node_file = File::load($node->{$field_name}->target_id);
-      $this->assertFileExists($node_file->getFileUri(), new FormattableMarkup('File exists after uploading a file (%filesize) under the max limit (%maxsize).', ['%filesize' => format_size($small_file->getSize()), '%maxsize' => $max_filesize]));
+      $this->assertFileExists($node_file->getFileUri());
       $this->assertFileEntryExists($node_file, new FormattableMarkup('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).
@@ -115,7 +115,7 @@ class FileFieldValidateTest extends FileFieldTestBase {
     $node_storage->resetCache([$nid]);
     $node = $node_storage->load($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file->getFileUri(), new FormattableMarkup('File exists after uploading a file (%filesize) with no max limit.', ['%filesize' => format_size($large_file->getSize())]));
+    $this->assertFileExists($node_file->getFileUri());
     $this->assertFileEntryExists($node_file, new FormattableMarkup('File entry exists after uploading a file (%filesize) with no max limit.', ['%filesize' => format_size($large_file->getSize())]));
   }
 
@@ -139,7 +139,7 @@ class FileFieldValidateTest extends FileFieldTestBase {
     $node_storage->resetCache([$nid]);
     $node = $node_storage->load($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file->getFileUri(), 'File exists after uploading a file with no extension checking.');
+    $this->assertFileExists($node_file->getFileUri());
     $this->assertFileEntryExists($node_file, 'File entry exists after uploading a file with no extension checking.');
 
     // Enable extension checking for text files.
@@ -158,7 +158,7 @@ class FileFieldValidateTest extends FileFieldTestBase {
     $node_storage->resetCache([$nid]);
     $node = $node_storage->load($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file->getFileUri(), 'File exists after uploading a file with extension checking.');
+    $this->assertFileExists($node_file->getFileUri());
     $this->assertFileEntryExists($node_file, 'File entry exists after uploading a file with extension checking.');
   }
 
@@ -181,7 +181,7 @@ class FileFieldValidateTest extends FileFieldTestBase {
     $node_storage->resetCache([$nid]);
     $node = $node_storage->load($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file->getFileUri(), 'File exists after uploading a file with no extension checking.');
+    $this->assertFileExists($node_file->getFileUri());
     $this->assertFileEntryExists($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 449c5a40738..fe1c6254091 100644
--- a/core/modules/file/tests/src/Functional/FileFieldWidgetTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldWidgetTest.php
@@ -89,7 +89,7 @@ class FileFieldWidgetTest extends FileFieldTestBase {
     $nid = $this->uploadNodeFile($test_file, $field_name, $type_name);
     $node = $node_storage->loadUnchanged($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file->getFileUri(), 'New file saved to disk on node creation.');
+    $this->assertFileExists($node_file->getFileUri());
 
     // Ensure the file can be downloaded.
     $this->drupalGet($node_file->createFileUrl());
@@ -263,7 +263,7 @@ class FileFieldWidgetTest extends FileFieldTestBase {
     $nid = $this->uploadNodeFile($test_file, $field_name, $type_name);
     $node = $node_storage->loadUnchanged($nid);
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file->getFileUri(), 'New file saved to disk on node creation.');
+    $this->assertFileExists($node_file->getFileUri());
 
     // Ensure the private file is available to the user who uploaded it.
     $this->drupalGet($node_file->createFileUrl());
@@ -330,7 +330,7 @@ class FileFieldWidgetTest extends FileFieldTestBase {
 
     $comment = Comment::load($cid);
     $comment_file = $comment->{'field_' . $name}->entity;
-    $this->assertFileExists($comment_file->getFileUri(), 'New file saved to disk on node creation.');
+    $this->assertFileExists($comment_file->getFileUri());
     // Test authenticated file download.
     $url = $comment_file->createFileUrl();
     $this->assertNotEqual($url, NULL, 'Confirmed that the URL is valid');
@@ -507,7 +507,7 @@ class FileFieldWidgetTest extends FileFieldTestBase {
 
     /** @var \Drupal\file\FileInterface $node_file */
     $node_file = File::load($node->{$field_name}->target_id);
-    $this->assertFileExists($node_file->getFileUri(), 'A file was saved to disk on node creation');
+    $this->assertFileExists($node_file->getFileUri());
     $this->assertEqual($attacker_user->id(), $node_file->getOwnerId(), 'New file belongs to the attacker.');
 
     // Ensure the file can be downloaded.
diff --git a/core/modules/migrate/tests/src/Kernel/process/DownloadTest.php b/core/modules/migrate/tests/src/Kernel/process/DownloadTest.php
index 9432c707edd..94c4a93e95b 100644
--- a/core/modules/migrate/tests/src/Kernel/process/DownloadTest.php
+++ b/core/modules/migrate/tests/src/Kernel/process/DownloadTest.php
@@ -40,7 +40,7 @@ class DownloadTest extends FileTestBase {
     // Test destructive download.
     $actual_destination = $this->doTransform($destination_uri);
     $this->assertSame($destination_uri, $actual_destination, 'Import returned a destination that was not renamed');
-    $this->assertFileNotExists('public://existing_file_0.txt', 'Import did not rename the file');
+    $this->assertFileNotExists('public://existing_file_0.txt');
   }
 
   /**
@@ -53,7 +53,7 @@ class DownloadTest extends FileTestBase {
     // Test non-destructive download.
     $actual_destination = $this->doTransform($destination_uri, ['file_exists' => 'rename']);
     $this->assertSame('public://another_existing_file_0.txt', $actual_destination, 'Import returned a renamed destination');
-    $this->assertFileExists($actual_destination, 'Downloaded file was created');
+    $this->assertFileExists($actual_destination);
   }
 
   /**
diff --git a/core/modules/migrate/tests/src/Kernel/process/FileCopyTest.php b/core/modules/migrate/tests/src/Kernel/process/FileCopyTest.php
index 22ac8f72a9f..4575db0d82c 100644
--- a/core/modules/migrate/tests/src/Kernel/process/FileCopyTest.php
+++ b/core/modules/migrate/tests/src/Kernel/process/FileCopyTest.php
@@ -67,10 +67,9 @@ class FileCopyTest extends FileTestBase {
     foreach ($data_sets as $data) {
       list($source_path, $destination_path) = $data;
       $actual_destination = $this->doTransform($source_path, $destination_path);
-      $message = sprintf('File %s exists', $destination_path);
-      $this->assertFileExists($destination_path, $message);
+      $this->assertFileExists($destination_path);
       // Make sure we didn't accidentally do a move.
-      $this->assertFileExists($source_path, $message);
+      $this->assertFileExists($source_path);
       $this->assertSame($actual_destination, $destination_path, 'The import returned the copied filename.');
     }
   }
@@ -152,10 +151,8 @@ class FileCopyTest extends FileTestBase {
     foreach ($data_sets as $data) {
       list($source_path, $destination_path) = $data;
       $actual_destination = $this->doTransform($source_path, $destination_path, ['move' => TRUE]);
-      $message = sprintf('File %s exists', $destination_path);
-      $this->assertFileExists($destination_path, $message);
-      $message = sprintf('File %s does not exist', $source_path);
-      $this->assertFileNotExists($source_path, $message);
+      $this->assertFileExists($destination_path);
+      $this->assertFileNotExists($source_path);
       $this->assertSame($actual_destination, $destination_path, 'The importer returned the moved filename.');
     }
   }
@@ -205,7 +202,7 @@ class FileCopyTest extends FileTestBase {
     $destination = $this->createUri('foo.txt', NULL, 'public');
     $expected_destination = 'public://foo_0.txt';
     $actual_destination = $this->doTransform($source, $destination, ['file_exists' => 'rename']);
-    $this->assertFileExists($expected_destination, 'File was renamed on import');
+    $this->assertFileExists($expected_destination);
     $this->assertSame($actual_destination, $expected_destination, 'The importer returned the renamed filename.');
   }
 
diff --git a/core/modules/user/tests/src/Functional/UserPictureTest.php b/core/modules/user/tests/src/Functional/UserPictureTest.php
index dff036b5baf..16fdfd41b24 100644
--- a/core/modules/user/tests/src/Functional/UserPictureTest.php
+++ b/core/modules/user/tests/src/Functional/UserPictureTest.php
@@ -94,7 +94,7 @@ class UserPictureTest extends BrowserTestBase {
     $this->assertNull(File::load($file->id()), 'File was removed from the database.');
     // Clear out PHP's file stat cache so we see the current value.
     clearstatcache(TRUE, $file->getFileUri());
-    $this->assertFileNotExists($file->getFileUri(), 'File was removed from the file system.');
+    $this->assertFileNotExists($file->getFileUri());
   }
 
   /**
diff --git a/core/tests/Drupal/KernelTests/Core/Theme/Stable9LibraryOverrideTest.php b/core/tests/Drupal/KernelTests/Core/Theme/Stable9LibraryOverrideTest.php
index 7ace13dd81f..073e0f41dcb 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/Stable9LibraryOverrideTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/Stable9LibraryOverrideTest.php
@@ -125,8 +125,8 @@ class Stable9LibraryOverrideTest extends KernelTestBase {
           $assert_path = str_replace("core/modules/$extension/", '', $clean_path);
 
           $this->assertEqual($expected_path, $stable_path, "$assert_path from the $extension/$library_name library is overridden in Stable 9.");
-          $this->assertFileExists("{$this->root}/$clean_path", "$clean_path exists.");
-          $this->assertFileExists("{$this->root}/$stable_path", "$stable_path exists.");
+          $this->assertFileExists("{$this->root}/$clean_path");
+          $this->assertFileExists("{$this->root}/$stable_path");
         }
       }
     }