public void CalcBracketLessExpressionTestMethod()
        {
            // arrange
            var expressionBracketsLess = "8/4+6-5-4";

            var performer = new OperationPerformer();

            // act
            var actualResult = performer.CalcBracketLessExpression(expressionBracketsLess);

            // assert
            Assert.AreEqual("-1", actualResult);
        }