iOptions Mock C# Unit Test

iOptions is a .NET library that simplifies reading and parsing configuration options in a .NET application. It provides a convenient way of reading options from JSON, XML, environment variables, and other sources.

In this guide, we will explore how to write unit tests for C# applications that use iOptions. We will be using the NUnit testing framework and Moq for mocking objects.

Setting up the Environment

Before we start writing unit tests for our iOptions application, we need to set up a few things:

1. Install the iOptions package via NuGet.

dotnet add package Microsoft.Extensions.Configuration
dotnet add package Microsoft.Extensions.Configuration.Json
dotnet add package Microsoft.Extensions.Configuration.Xml
dotnet add package Microsoft.Extensions.Configuration.EnvironmentVariables

2. Install the NUnit and Moq packages via NuGet.

dotnet add package NUnit
dotnet add package Moq

Writing Unit Tests

Mocking IConfiguration

In this example, we will be testing a Calculator class that uses iOptions to read the configuration values. The configuration values are read from a JSON file.

First, we need to create a mock of IConfiguration, which is provided by the iOptions library.

[TestFixture]
public class CalculatorTests
{
    private Mock<IConfiguration> _configuration;

    [SetUp]
    public void Setup()
    {
        _configuration = new Mock<IConfiguration>();
    }

    [Test]
    public void TestAddition()
    {
        // arrange
        _configuration.Setup(x => x["Calculator:Operand1"]).Returns("10");
        _configuration.Setup(x => x["Calculator:Operand2"]).Returns("5");
        var calculator = new Calculator(_configuration.Object);

        // act
        var result = calculator.Addition();

        // assert
        Assert.AreEqual(15, result);
    }
}

In the test above, we set up the mock object to return the desired configuration values when they are accessed. We then initialize the Calculator class with the mocked IConfiguration object and execute the Addition method. Finally, we verify that the result of the operation is correct.

Using IConfigurationBuilder

In this example, we will be testing a WeatherForecast class that reads the configuration values from multiple sources using IConfigurationBuilder. We will mock the IConfigurationRoot object that is returned by the builder.

[TestFixture]
public class WeatherForecastTests
{
    private Mock<IConfigurationRoot> _configuration;

    [SetUp]
    public void Setup()
    {
        var builder = new ConfigurationBuilder();
        builder.AddInMemoryCollection(new Dictionary<string, string>()
        {
            {"WeatherForecast:Summary", "Sunny"},
            {"WeatherForecast:Temperature", "25"}
        });
        var configuration = builder.Build();

        _configuration = new Mock<IConfigurationRoot>();
        _configuration.Setup(x => x.GetSection("WeatherForecast")).Returns(configuration.GetSection("WeatherForecast"));
    }

    [Test]
    public void TestSummary_ReturnsExpectedValue()
    {
        // arrange
        var weatherForecast = new WeatherForecast(_configuration.Object);

        // act
        var result = weatherForecast.Summary;

        // assert
        Assert.AreEqual("Sunny", result);
    }

    [Test]
    public void TestTemperature_ReturnsExpectedValue()
    {
        // arrange
        var weatherForecast = new WeatherForecast(_configuration.Object);

        // act
        var result = weatherForecast.Temperature;

        // assert
        Assert.AreEqual(25, result);
    }
}

In the test above, we first create an instance of IConfigurationRoot by building an instance of IConfigurationBuilder. We then set up a mock object to return the desired configuration values when they are accessed. We initialize the WeatherForecast class with the mocked IConfigurationRoot object and execute the methods that read the configuration values. Finally, we verify that the correct values are returned.

Conclusion

In this guide, we learned how to write unit tests for iOptions applications using the NUnit testing framework and Moq for mocking objects. We saw how to mock IConfiguration and IConfigurationRoot objects and execute methods that read configuration values from different sources. Writing unit tests for iOptions applications allows us to ensure that our code is behaving as expected and handling different configuration scenarios correctly.