# Unit Testing in VB.NET

# Unit Testing for Tax Calculation

This example is divided into two pillars

  • SalaryCalculation Class : Calculating the net salary after tax deduction
  • SalaryCalculationTests Class : For testing the method that calculates the net salary

Step 1: Create Class Library, name it WagesLibrary or any appropriate name. Then rename the class to SalaryCalculation

''' ''' Class for Salary Calculations ''' Public Class SalaryCalculation


   ''' <summary>
    ''' Employee Salary
    ''' </summary>
    Public Shared Salary As Double

    ''' <summary>
    ''' Tax fraction (0-1)
    ''' </summary>
    Public Shared Tax As Double

    ''' <summary>
    ''' Function to calculate Net Salary
    ''' </summary>
    ''' <returns></returns>
    Public Shared Function CalculateNetSalary()
        Return Salary - Salary * Tax
    End Function
End Class

Step 2 : Create Unit Test Project. Add reference to the created class library and paste the below code

Imports WagesLibrary 'Class library you want to test

''' <summary>
''' Test class for testing SalaryCalculation
''' </summary>
<TestClass()> Public Class SalaryCalculationTests

    ''' <summary>
    ''' Test case for the method CalculateNetSalary
    ''' </summary>
    <TestMethod()> Public Sub CalculateNetSalaryTest()
        SalaryCalculation.Salary = 100
        SalaryCalculation.Tax = 0.1
        Assert.AreEqual(90.0, SalaryCalculation.CalculateNetSalary(), 0.1)
    End Sub
End Class

Assert.Equal checks the expected value against the actual calculated value. the value 0.1 is used to allow tolerance or variation between expected and actual result.

Step 3 : Run the test of the method to see result enter image description here

Test result enter image description here

# Testing Employee Class assigned and derived Properties

This example has more tests available in unit testing.

Employee.vb (Class Library)

''' <summary>
''' Employee Class
''' </summary>
Public Class Employee

    ''' <summary>
    ''' First name of employee
    ''' </summary>
    Public Property FirstName As String = ""

    ''' <summary>
    ''' Last name of employee
    ''' </summary>
    Public Property LastName As String = ""

    ''' <summary>
    ''' Full name of employee
    ''' </summary>
    Public ReadOnly Property FullName As String = ""

    ''' <summary>
    ''' Employee's age
    ''' </summary>
    Public Property Age As Byte

    ''' <summary>
    ''' Instantiate new instance of employee
    ''' </summary>
    ''' <param name="firstName">Employee first name</param>
    ''' <param name="lastName">Employee last name</param>
    Public Sub New(firstName As String, lastName As String, dateofbirth As Date)
        Me.FirstName = firstName
        Me.LastName = lastName
        FullName = Me.FirstName + " " + Me.LastName
        Age = Convert.ToByte(Date.Now.Year - dateofbirth.Year)
    End Sub
End Class

EmployeeTest.vb (Test Project)

Imports HumanResources

<TestClass()>
Public Class EmployeeTests
    ReadOnly _person1 As New Employee("Waleed", "El-Badry", New DateTime(1980, 8, 22))
    ReadOnly _person2 As New Employee("Waleed", "El-Badry", New DateTime(1980, 8, 22))

    <TestMethod>
    Public Sub TestFirstName()
        Assert.AreEqual("Waleed", _person1.FirstName, "First Name Mismatch")
    End Sub

    <TestMethod>
    Public Sub TestLastName()
        Assert.AreNotEqual("", _person1.LastName, "No Last Name Inserted!")
    End Sub

    <TestMethod>
    Public Sub TestFullName()
        Assert.AreEqual("Waleed El-Badry", _person1.FullName, "Error in concatination of names")
    End Sub

    <TestMethod>
    Public Sub TestAge()
        Assert.Fail("Age is not even tested !") 'Force test to fail !
        Assert.AreEqual(Convert.ToByte(36), _person1.Age)
    End Sub

    <TestMethod>
    Public Sub TestObjectReference()
        Assert.AreSame(_person1.FullName, _person2.FullName, "Different objects with same data")
    End Sub
End Class

Result after running tests

enter image description here

enter image description here

# Remarks

This is the simplest yet descriptive example for the unit testing procedure. Feel free to add more methods to check against different data types.