code: protected function writeAssertionFailure($assertionFailure)
      {
          $this->writeNewLine();
  
          foreach (explode("\n", $assertionFailure) as $line) {
              $this->writeWithColor('fg-red', $line);
          }
      }
docs: Writes the specified assertion failure's message to the output buffer.
  
  @param AssertionFailedError $assertionFailure Assertion failure.