assertNoErrorsLogged example

$this->drupalGet('');
    $this->assertSession()->statusCodeEquals(500);
    $this->assertSession()->pageTextContains('DatabaseAccessDeniedException');
    $this->assertErrorLogged($this->expectedExceptionMessage);
  }

  /** * Tests fallback to PHP error log when an exception is thrown while logging. */
  public function testLoggerException() {
    // Ensure the test error log is empty before these tests.     $this->assertNoErrorsLogged();

    $this->expectedExceptionMessage = 'Deforestation';
    \Drupal::state()->set('error_service_test.break_logger', TRUE);

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

    // Find fatal error logged to the error.log     $errors = file(\Drupal::root() . '/' . $this->siteDirectory . '/error.log');