drupalLogOut example

$nid = $this->uploadNodeFile($test_file, $field_name, $type_name, TRUE, ['private' => TRUE]);
    \Drupal::entityTypeManager()->getStorage('node')->resetCache([$nid]);
    /** @var \Drupal\node\NodeInterface $node */
    $node = $node_storage->load($nid);
    $node_file = File::load($node->{$field_name}->target_id);
    // Ensure the file can be viewed.     $this->drupalGet('node/' . $node->id());
    $this->assertSession()->responseContains($node_file->getFilename());
    // Ensure the file can be downloaded.     $this->drupalGet($node_file->createFileUrl(FALSE));
    $this->assertSession()->statusCodeEquals(200);
    $this->drupalLogOut();
    // Ensure the file cannot be downloaded after logging out.     $this->drupalGet($node_file->createFileUrl(FALSE));
    $this->assertSession()->statusCodeEquals(403);

    // Create a field with no view access. See     // field_test_entity_field_access().     $no_access_field_name = 'field_no_view_access';
    $this->createFileField($no_access_field_name, 'node', $type_name, ['uri_scheme' => 'private']);
    // Test with the field that should deny access through field access.     $this->drupalLogin($this->adminUser);
    $nid = $this->uploadNodeFile($test_file, $no_access_field_name, $type_name, TRUE, ['private' => TRUE]);