diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeExecuteTestBase.php b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeExecuteTestBase.php
index dbe67abc1b..472a0de94a 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeExecuteTestBase.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeExecuteTestBase.php
@@ -170,11 +170,13 @@ public function testMigrateUpgradeExecute() {
   }
 
   /**
-   * Gets the source base path for private files the concrete test.
+   * Provides the source base path for private files for the credential form.
    *
    * @return string
    *   The source base path.
    */
-  abstract protected function getSourcePrivateBasePath();
+  protected function getSourcePrivateBasePath() {
+    return NULL;
+  }
 
 }
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php
index 75e1b2d785..f8ae8f1e24 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php
@@ -267,7 +267,8 @@ protected function assertFileMigrations() {
     $fs = \Drupal::service('file_system');
     $files = $this->getManagedFiles();
     foreach ($files as $file) {
-      $scheme = preg_replace('/:.*/', '', $file['uri']);
+      preg_match('/^(private|public|temporary):/', $file['uri'], $matches);
+      $scheme = $matches[1];
       $filepath = $fs->realpath($file['uri']);
       if ($scheme === 'temporary') {
         $this->assertFileNotExists($filepath);
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/d7/FilePathTest.php b/core/modules/migrate_drupal_ui/tests/src/Functional/d7/FilePathTest.php
index 0d3158ffe0..eaa62a3b42 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/d7/FilePathTest.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/d7/FilePathTest.php
@@ -3,7 +3,6 @@
 namespace Drupal\Tests\migrate_drupal_ui\Functional\d7;
 
 use Drupal\Core\File\FileSystemInterface;
-use Drupal\migrate\MigrateException;
 use Drupal\Tests\migrate_drupal_ui\Functional\MigrateUpgradeTestBase;
 
 /**
@@ -214,9 +213,9 @@ protected function makeFiles() {
     // Get file information from the source database.
     $files = $this->getManagedFiles();
     foreach ($files as $file) {
-      $scheme = preg_replace('/:.*/', '', $file['uri']);
-
-      $path = isset($this->variable[$scheme]) ? $this->variable[$scheme] : '';
+      preg_match('/^(private|public|temporary):/', $file['uri'], $matches);
+      $scheme = $matches[1];
+      $path = $this->variable[$scheme] ?: '';
       $base_path = $this->getSourcePath($scheme) . '/' . $path;
       $filepath = $base_path . '/' . $file['filename'];
       // Create the file.
@@ -224,16 +223,10 @@ protected function makeFiles() {
       if (!$source_file) {
         // If fopen didn't work, make sure there's a writable directory in
         // place.
-        $this->fs = \Drupal::service('file_system');
         $dir = $this->fs->dirname($filepath);
-        if (!$this->fs->prepareDirectory($dir, FileSystemInterface:: CREATE_DIRECTORY | FileSystemInterface::MODIFY_PERMISSIONS)) {
-          throw new MigrateException("Could not create or write to directory '$dir'");
-        }
+        $this->fs->prepareDirectory($dir, FileSystemInterface:: CREATE_DIRECTORY | FileSystemInterface::MODIFY_PERMISSIONS);
         // Let's try that fopen again.
         $source_file = @fopen($filepath, 'w');
-        if (!$source_file) {
-          throw new MigrateException("Could not write to file '$filepath'");
-        }
       }
       fwrite($source_file, '42');
     }
@@ -246,7 +239,7 @@ protected function makeFiles() {
    *   The file scheme.
    */
   public function getSourcePath($scheme) {
-    $base_path = isset($this->basePath[$scheme]) ? $this->basePath[$scheme] : '';
+    $base_path = $this->basePath[$scheme] ?: '';
     // Puts the source files in the site temp directory.
     return $this->tempFilesDirectory . '/' . $base_path;
   }
@@ -308,10 +301,4 @@ protected function getMissingPaths() {
   protected function getSourceBasePath() {
   }
 
-  /**
-   * {@inheritdoc}
-   */
-  protected function getSourcePrivateBasePath() {
-  }
-
 }
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/d7/Upgrade7Test.php b/core/modules/migrate_drupal_ui/tests/src/Functional/d7/Upgrade7Test.php
index 3f94cf66aa..ab8a75be64 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/d7/Upgrade7Test.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/d7/Upgrade7Test.php
@@ -74,17 +74,6 @@ protected function getSourcePrivateBasePath() {
     return __DIR__ . '/files';
   }
 
-  /**
-   * {@inheritdoc}
-   */
-  protected function getFilenames() {
-    return [
-      'public' => ['cube.jpeg', 'ds9.txt'],
-      'private' => ['Babylon5.txt'],
-      'temporary' => ['TerokNor.txt'],
-    ];
-  }
-
   /**
    * {@inheritdoc}
    */