Tests Everywhere - .NET C#

Published at

11/22/2023

rogervinas / tests-everywhere

🤠 Tests, Tests Everywhere!

.NET C# testing this simple Hello World with NUnit and Moq

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- Implementation
- Test
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Implementation

Create HelloMessage interface and HelloWorldMessage implementing it in HelloMessage.cs:

public interface HelloMessage
{
  public String Text {
    get;
  }
}

public class HelloWorldMessage : HelloMessage
{
  public string Text {
    get {
      return "Hello World!";
    }
  }
}

Creating it as an interface will allow us to mock it for testing using Moq which does not support mocking final classes. Maybe other libraries support that but using an interface is simpler.

Same way create HelloConsole interface and HelloSystemConsole class implementing it in HelloConsole.cs:

public interface HelloConsole {
  void Print(String text);
}

public class HelloSystemConsole : HelloConsole
{
  public void Print(String text) {
    Console.WriteLine(text);
  }
}

Create HelloApp in HelloApp.cs:

public class HelloApp
{
  private HelloMessage message;
  private HelloConsole console;

  public HelloApp(HelloMessage message, HelloConsole console) {
    this.message = message;
    this.console = console;
  }

  public void PrintHello() {
    console.Print(message.Text);
  }
}

Create main Hello.Main/Program.cs that wraps it all together:

var message = new HelloWorldMessage();
var console = new HelloSystemConsole();
var app = new HelloApp(message, console);
app.PrintHello();

Test

Following NUnit > Writing Tests and Moq guides ...

Test HelloMessage in HelloMessageTest.cs:

[Test]
public void ShouldReturnHelloWorld()
{
  var message = new HelloWorldMessage();
  Assert.That(message.Text, Is.EqualTo("Hello World!"));
}

Test HelloApp in HelloAppTest.cs:

[Test]
public void ShouldPrintHelloMessage()
{
  var messageText = "Hello Test!";

  // 2.1 Create a mock of HelloMessage
  var messageMock = new Mock<HelloMessage>();
  // 2.2 Expect HelloMessage mock to receive a call to Text
  // and return "Hello Test!"
  messageMock.Setup(message => message.Text).Returns(messageText);
  // 2.3 Get the mock object to pass it to HelloApp
  var message = messageMock.Object;

  // 2.4 Create a mock of HelloConsole
  var consoleMock = new Mock<HelloConsole>();
  // 2.5 No need to set expectations for this one
  // 2.6 Get the mock object to pass it to HelloApp
  var console = consoleMock.Object;

  // 2.3 Create a HelloApp, the one we want to test, passing the mocks
  var app = new HelloApp(message, console);
  // 2.4 Execute the method we want to test
  app.PrintHello();

  // 2.5 Verify HelloConsole mock Print() method
  // has been called once with "Hello Test!"
  consoleMock.Verify(console => console.Print(messageText), Times.Once);
}

Test output should look like:

NUnit Adapter 4.2.0.0: Test execution complete
  Passed ShouldPrintHelloMessage [180 ms]
  Passed ShouldReturnHelloWorld [7 ms]

Test Run Successful.
Total tests: 2
     Passed: 2
 Total time: 2.7702 Seconds

Happy Testing! 💙