public void TestMathExpression_ShouldProvideCorrectSum() { // Arrange var calcService = new CalculatorService(); var controller = new CalculatorController(calcService); // Act var expression = controller.EvaluateExpression(new MathExpression { Expression = "2+4" }); var contentResult = expression as OkNegotiatedContentResult <MathExpression>; // Assert Assert.IsNotNull(contentResult); Assert.IsNotNull(contentResult.Content); // Assert.IsTrue(contentResult.Content.Key.HasValue); Assert.AreEqual(6, contentResult.Content.Key); }