Testing ASP.NET Core Applications

Introduction

Testing is a crucial part of the development process in ASP.NET Core applications. It ensures that the application behaves as expected and helps identify and fix bugs early in the development cycle.

Unit Testing

Unit tests verify that individual components of an application work as expected. In ASP.NET Core, you can use testing frameworks like xUnit, MSTest, or NUnit. Below is an example of a unit test using xUnit.

using System;
using Xunit;

public class CalculatorTests
{
    [Fact]
    public void Add_ReturnsSum()
    {
        // Arrange
        var calculator = new Calculator();
        int a = 5;
        int b = 3;

        // Act
        int result = calculator.Add(a, b);

        // Assert
        Assert.Equal(8, result);
    }
}

public class Calculator
{
    public int Add(int a, int b)
    {
        return a + b;
    }
}

Integration Testing

Integration tests ensure that different parts of the application work together as expected. ASP.NET Core provides a TestServer class to create an in-memory test server for integration tests.

using System.Net.Http;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.TestHost;
using Xunit;

public class IntegrationTests
{
    private readonly TestServer _server;
    private readonly HttpClient _client;

    public IntegrationTests()
    {
        _server = new TestServer(new WebHostBuilder()
            .UseStartup<Startup>());
        _client = _server.CreateClient();
    }

    [Fact]
    public async Task Get_EndpointsReturnSuccessAndCorrectContentType()
    {
        var response = await _client.GetAsync("/api/values");

        response.EnsureSuccessStatusCode(); // Status Code 200-299
        Assert.Equal("application/json; charset=utf-8",
            response.Content.Headers.ContentType.ToString());
    }
}

End-to-End Testing

End-to-end (E2E) tests simulate real user scenarios to ensure that the entire application works correctly. Tools like Selenium or Playwright can be used for E2E testing.

using System.Threading.Tasks;
using Microsoft.Playwright;
using Xunit;

public class E2ETests
{
    [Fact]
    public async Task Homepage_ShouldLoadSuccessfully()
    {
        using var playwright = await Playwright.CreateAsync();
        var browser = await playwright.Chromium.LaunchAsync(new BrowserTypeLaunchOptions { Headless = true });
        var page = await browser.NewPageAsync();
        await page.GotoAsync("https://localhost:5001");

        var title = await page.TitleAsync();
        Assert.Equal("Home Page - My ASP.NET Core Application", title);
    }
}

Conclusion

Testing ASP.NET Core applications involves unit tests, integration tests, and end-to-end tests. By thoroughly testing your application, you can ensure its reliability and performance, leading to a better user experience.