13.3. Lab: Unit Test

13.3.1. Your Tasks

1. Implement this unit testing project.

2. Add one method in the application and one corresponding test in the test project.

3. As usual, prepare the assignment using a Word document with screenshots (code and execution with path and username) and your annotations.

13.3.2. Preparing Project

The idea of TDD is to write tests first, so that you will be focused with the requirements and not to be distracted by your own coding. That’s why we start with simple test cases in the test project to test the units in the application project. After you make sure the application tests can pass, you then improve the units (methods, classes) in the application project.

The process of creating a unit test involves several steps. Most, if not all, of the steps can be performed in VS Code but it can be easier from time to time with the terminal:

1. Create a lab folder, call it Ch13SelectedTopicsLab. Its location is inside [USERNAME]\workspace\introcscs\.

2. Create a solution folder:

   1. Inside your Ch13SelectedTopicsLab, create a folder, call it UnitTestProject1 (mkdir UnitTestProject1).

   To make this folder a solution, run:

   tychen@mac:~/workspace/introcscs/Ch13SelectedTopicsLab/UnitTestProject1$ dotnet new sln
   The template "Solution File" was created successfully.
   

   2. Later, when you need to choose a solution for the active project, go to View ==> Command Palette ==> type solution and choose .NET: Open Solution to choose your solution, which is UnitTestProject1 in this case.

3. Create an application project folder (new here but can be existing), call it MathApp, and

   a test project folder, call it MathAppTest:

   1. mkdir MathApp inside UnitTestProject1.

   2. mkdir MathAppTest inside UnitTestProject1.

   Now if you ls, you should see both folders.

4. Make MathApp a console app project and MathAppTest a MSTest project:

   1. Inside the MathApp folder, do dotnet new console.

   2. Inside the MathAppTest folder, do dotnet new mstest (we are using MSTest here but you can use other tools such as NUnit or xUnit).

5. Add both projects to solution:

   1. Add MathApp to solution:

   tychen@mac:~/workspace/introcscs/Ch13SelectedTopicsLab/UnitTestProject1$ dotnet sln add MathApp
   Project `MathApp/MathApp.csproj` added to the solution.
   

   2. Add MathAppTest to the solution:

   tychen@mac:~/workspace/introcscs/Ch13SelectedTopicsLab/UnitTestProject1$ dotnet sln add MathAppTest/
   Project `MathAppTest/MathAppTest.csproj` added to the solution.
   

6. Add the app project to the test project as one of the projects to be tested:

   dotnet add [location of your test csproj file] reference [location of the csproj file for project to be tested]
   

   For example, inside the UnitTestProject1 folder, issue dotnet add MathAppTest reference MathApp. You should see:

   tychen@mac:~/workspace/introcscs/Ch13SelectedTopicsLab/UnitTestProject1$ dotnet add MathAppTest reference MathApp
   Reference `..\MathApp\MathApp.csproj` added to the project.
   

13.3.3. Preparing Code

In your application folder, we know there is a default Program.cs file created when we run dotnet new console. Same thing, when we run dotnet new mstest, there is a UnitTest1 created automatically for you to use. Now revise the content of the two files.

The content of the console app Program.cs in your MathApp folder should look like the code below, filled with a class BasicMath containing 4 basic arithmetic operation methods (note that the namespace is critical for the test project to access this app project):

namespace SomeMath
{

    internal class Program
    {
        private static void Main(string[] args)
        {
            Console.WriteLine("Hello, World!");
        }
    }

    public class BasicMath
    {
        public double Add(double num1, double num2)
        {
            return num1 + num2;
        }

        public double Subtract(double num1, double num2)
        {
            return num1 - num2;
        }

        public double divide(double num1, double num2)
        {
            return num1 / num2;
        }

        public double Multiply(double num1, double num2)
        {
            // To trace error while testing, writing + operator instead of * operator.
            return num1 + num2;         ///// this will fail!!!!!
        }
    }
}

You would want to run dotnet build in the app project folder to make sure there is no errors:

dotnet build

The content of the UnitTest1 file in the MathAppTest folder, on the other hand, should look like this (note the Assert method works in debug compilation to take in a Boolean condition as a parameter, and shows the error dialog if the condition is false):

using SomeMath;             ///// we want to talk to the BasicMath class

namespace MathAppTest;      ///// generated when creating project

[TestClass]                 ///// specify the UNIT (class) to be tested
public class UnitTest1
{
    [TestMethod]            ///// specify the UNIT (method) to be tested
    public void Test_AddMethod()
    {
        BasicMath bm = new BasicMath();     // create instance
        double res = bm.Add(10, 10);        // run the method
        Assert.AreEqual(res, 20);           // detect if the answers match
    }

    [TestMethod]
    public void Test_SubtractMethod()
    {
        BasicMath bm = new BasicMath();
        double res = bm.Subtract(10, 10);
        Assert.AreEqual(res, 0);
    }

    [TestMethod]
    public void Test_DivideMethod()
    {
        BasicMath bm = new BasicMath();
        double res = bm.divide(10, 5);
        Assert.AreEqual(res, 2);
    }

    [TestMethod]
    public void Test_MultiplyMethod()
    {
        BasicMath bm = new BasicMath();
        double res = bm.Multiply(10, 10);
        Assert.AreEqual(res, 100);
    }
}

You would want to run dotnet build in the test project folder to make sure there is no errors:

dotnet build

Now if you run dotnet test inside UnitTestProject1, you should see the results like:

tychen@mac:~/workspace/introcscs/Ch13SelectedTopics/UnitTestProject1$ dotnet test
Determining projects to restore...
All projects are up-to-date for restore.
MathApp -> /Users/tychen/workspace/introcscs/Ch13SelectedTopics/UnitTestProject1/MathApp/bin/Debug/net8.0/MathApp.dll
MathAppTest -> /Users/tychen/workspace/introcscs/Ch13SelectedTopics/UnitTestProject1/MathAppTest/bin/Debug/net8.0/MathAppTest.dll
Test run for /Users/tychen/workspace/introcscs/Ch13SelectedTopics/UnitTestProject1/MathAppTest/bin/Debug/net8.0/MathAppTest.dll (.NETCoreApp,Version=v8.0)
Microsoft (R) Test Execution Command Line Tool Version 17.9.0 (x64)
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
A total of 1 test files matched the specified pattern.
Failed Test_MultiplyMethod [42 ms]
Error Message:
    Assert.AreEqual failed. Expected:<20>. Actual:<100>.
Stack Trace:
    at MathAppTest.UnitTest1.Test_MultiplyMethod() in /Users/tychen/workspace/introcscs/Ch13SelectedTopics/UnitTestProject1/MathAppTest/UnitTest1.cs:line 37
    at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
    at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)


Failed!  - Failed:     1, Passed:     3, Skipped:     0, Total:     4, Duration: 118 ms - MathAppTest.dll (net8.0)

13.3.4. Run Testing in VS Code

You should also be able to run the test using VS Code for better visualization of the tests. You may need to install an extension such as C# Dev Kit for the purpose and build/rebuild the test project in Test Explorer to make the tests show up in Testing section of the Activity Bar.