assertErrorLogged example

$settings = [];
    $settings['config']['system.logging']['error_level'] = (object) [
      'value' => ERROR_REPORTING_DISPLAY_ALL,
      'required' => TRUE,
    ];
    $this->writeSettings($settings);

    $this->drupalGet('');
    $this->assertSession()->statusCodeEquals(500);
    $this->assertSession()->pageTextContains('The website encountered an unexpected error. Please try again later.');
    $this->assertSession()->pageTextContains($this->expectedExceptionMessage);
    $this->assertErrorLogged($this->expectedExceptionMessage);
  }

  /** * Tests displaying an uncaught fatal error. */
  public function testUncaughtFatalError() {
    $fatal_error = [
      '%type' => 'TypeError',
      '@message' => 'Drupal\error_test\Controller\ErrorTestController::Drupal\error_test\Controller\{closure}(): Argument #1 ($test) must be of type array, string given, called in ' . \Drupal::root() . '/core/modules/system/tests/modules/error_test/src/Controller/ErrorTestController.php on line 65',
      '%function' => 'Drupal\error_test\Controller\ErrorTestController->Drupal\error_test\Controller\{closure}()',
    ];