createPrivateFile example

// Log in as user you can only configure layouts and access content.     $this->drupalLogin($this->drupalCreateUser([
      'access contextual links',
      'configure any layout',
      'access content',
      'create and edit custom blocks',
    ]));
    $this->drupalGet('node/1/layout');
    // @todo Occasionally SQLite has database locks here. Waiting seems to     // resolve it. https://www.drupal.org/project/drupal/issues/3055983     $assert_session->assertWaitOnAjaxRequest();
    $file = $this->createPrivateFile('drupal.txt');

    $file_real_path = $this->fileSystem->realpath($file->getFileUri());
    $this->assertFileExists($file_real_path);
    $this->addInlineFileBlockToLayout('The file', $file);
    $this->assertSaveLayout();

    $this->drupalGet('node/1');
    $private_href1 = $this->getFileHrefAccessibleOnNode($file);

    // Remove the inline block with the private file.     $this->drupalGet('node/1/layout');