public RunSpecification()
        {
            message = new StringBuilderTextLineWriter();

            writer = new StringTestOutputWriter(
                new HumanFriendlyFormatter(),
                message);
        }
        public RunSpecification(ITestOutputWriter writer)
        {
            if (writer == null)
            {
                throw new ArgumentNullException(nameof(writer));
            }

            _message = new StringBuilderTextLineWriter();
            _writer  = new CombinedTestOutputWriter(new List <ITestOutputWriter>()
            {
                writer, new StringTestOutputWriter(new HumanFriendlyFormatter(), _message)
            });
        }