{"id":2258,"date":"2025-09-18T13:13:52","date_gmt":"2025-09-18T13:13:52","guid":{"rendered":"https:\/\/www.cmarix.com\/qanda\/?p=2258"},"modified":"2026-02-05T11:59:18","modified_gmt":"2026-02-05T11:59:18","slug":"unit-integration-testing-modular-monolith-dotnet","status":"publish","type":"post","link":"https:\/\/www.cmarix.com\/qanda\/unit-integration-testing-modular-monolith-dotnet\/","title":{"rendered":"How to Perform Unit and Integration Testing in Modular Monoliths (.NET)?"},"content":{"rendered":"\n

Modular monoliths in .NET let you structure your application as distinct modules like Product, Order, and User without breaking it into separate services. Testing in this setup isn’t just helpful, it’s necessary. Unit tests are important to check how each module behaves in isolation, while integration tests are important to see if they work together as intended in real scenarios.<\/p>\n\n\n\n

Types of Tests in Modular Monolith<\/h2>\n\n\n\n
Test Type<\/strong><\/td>What it Tests<\/strong><\/td>Scope<\/strong><\/td><\/tr>
Unit Test<\/td>Individual classes\/methods<\/td>Internal logic<\/td><\/tr>
Integration Test<\/td>Interaction between modules or with real database<\/td>System workflows<\/td><\/tr>
End-to-End Test (optional)<\/td>Full app (UI\/API to DB)<\/td>External behavior<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Example App Folder Structure<\/h4>\n\n\n\n
MyApp\/\n\u251c\u2500\u2500 Modules\/\n\u2502   \u251c\u2500\u2500 Product\/\n\u2502   \u2502   \u251c\u2500\u2500 ProductService.cs\n\u2502   \u2502   \u2514\u2500\u2500 ProductRepository.cs\n\u2502   \u251c\u2500\u2500 Order\/\n\u2502   \u2502   \u2514\u2500\u2500 OrderService.cs\n\u251c\u2500\u2500 API\/\n\u2502   \u2514\u2500\u2500 Controllers\/\n\u251c\u2500\u2500 Tests\/\n\u2502   \u251c\u2500\u2500 UnitTests\/\n\u2502   \u2514\u2500\u2500 IntegrationTests\/<\/code><\/pre>\n\n\n\n
How to Conduct Unit Testing in Modular Monolith .NET (Step-by-Step)<\/h2>\n\n\n\n
Step 1: Add xUnit and Moq to your test project<\/h3>\n\n\n\n
dotnet add package xunit\ndotnet add package Moq<\/code><\/pre>\n\n\n\n
Step 2: Create Unit Test for Product Module<\/h3>\n\n\n\n
ProductService.cs<\/strong><\/p>\n\n\n\n
public class ProductService\n{\n    private readonly IProductRepository _repo;\n    public ProductService(IProductRepository repo)\n    {\n        _repo = repo;\n    }\n\n    public Product GetById(int id) => _repo.GetById(id);\n}<\/code><\/pre>\n\n\n\n
ProductServiceTests.cs<\/strong><\/p>\n\n\n\n
public class ProductServiceTests\n{\n    [Fact]\n    public void GetById_ShouldReturnProduct()\n    {\n        \/\/ Arrange\n        var mockRepo = new Mock<IProductRepository>();\n        mockRepo.Setup(x => x.GetById(1)).Returns(new Product { Id = 1, Name = \"Test\" });\n\n        var service = new ProductService(mockRepo.Object);\n\n        \/\/ Act\n        var result = service.GetById(1);\n\n        \/\/ Assert\n        Assert.NotNull(result);\n        Assert.Equal(\"Test\", result.Name);\n    }\n}<\/code><\/pre>\n\n\n\n
Integration Testing in Modular Monolith (Step-by-Step)<\/h2>\n\n\n\n
Step 1: Add Required NuGet Packages<\/h3>\n\n\n\n
dotnet add package Microsoft.AspNetCore.Mvc.Testing\ndotnet add package Microsoft.EntityFrameworkCore.InMemory\ndotnet add package FluentAssertions<\/code><\/pre>\n\n\n\n
Step 2: Create In-Memory Test Server<\/h3>\n\n\n\n
\u00a0ProductIntegrationTests.cs<\/h4>\n\n\n\n
public class ProductIntegrationTests : IClassFixture<WebApplicationFactory<Program>>\n{\n    private readonly HttpClient _client;\n\n    public ProductIntegrationTests(WebApplicationFactory<Program> factory)\n    {\n        _client = factory.CreateClient(); \/\/ In-memory test server\n    }\n\n    [Fact]\n    public async Task GetProductById_ReturnsProduct()\n    {\n        \/\/ Act\n        var response = await _client.GetAsync(\"\/api\/products\/1\");\n        response.EnsureSuccessStatusCode();\n\n        var json = await response.Content.ReadAsStringAsync();\n        var product = JsonConvert.DeserializeObject<Product>(json);\n\n        \/\/ Assert\n        product.Should().NotBeNull();\n        product.Id.Should().Be(1);\n    }\n}<\/code><\/pre>\n\n\n\n
Purpose:<\/strong> This tests the real behavior of the app, with routing, controllers, and DB (in-memory).<\/p>\n\n\n\n
Step 3: Configure In-Memory DB in Program.cs for testing<\/h3>\n\n\n\n
if (app.Environment.IsEnvironment(\"Testing\"))\n{\n    builder.Services.AddDbContext<AppDbContext>(options =>\n        options.UseInMemoryDatabase(\"TestDb\"));\n}<\/code><\/pre>\n\n\n\n
Or override it using WebApplicationFactory<T> in your test setup.<\/p>\n\n\n\n
Best Practices for all Testing in Modular Monolith<\/h2>\n\n\n\n
Aspect<\/strong><\/td>Recommendation<\/strong><\/td><\/tr>
Unit Tests<\/td>Fast, mock dependencies, and cover edge cases<\/td><\/tr>
Integration Tests<\/td>Use TestServer, real or in-memory databases<\/td><\/tr>
Foldering<\/td>Organize tests by module for clarity<\/td><\/tr>
Test Boundaries<\/strong><\/td>Verify communication between modules is correct<\/td><\/tr>
Isolation<\/td>Clean the database before each integration test<\/td><\/tr>
Performance<\/td>Keep integration tests fewer, but focused and meaningful<\/td><\/tr>
Naming<\/td>Follow naming like ProductServiceTests.cs or OrderIntegrationTests.cs<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
Final Thought<\/h2>\n\n\n\n
Unit tests help confirm that each module works as intended, while integration tests ensure different modules interact properly in real-world scenarios. If you’re building a modular monolith and want reliable, scalable testing strategies, it\u2019s a smart move to hire .NET developers<\/a> who understand how to balance isolation with real-world validation. That\u2019s how you keep your application modular, maintainable, and production-ready.<\/p>\n","protected":false},"excerpt":{"rendered":"
Modular monoliths in .NET let you structure your application as distinct modules like Product, Order, and User without breaking it into separate services. Testing in this setup isn’t just helpful, it’s necessary. Unit tests are important to check how each module behaves in isolation, while integration tests are important to see if they work together […]<\/p>\n","protected":false},"author":2,"featured_media":2259,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[4,3],"tags":[],"class_list":["post-2258","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-dot-net","category-web"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.cmarix.com\/qanda\/wp-json\/wp\/v2\/posts\/2258","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.cmarix.com\/qanda\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.cmarix.com\/qanda\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.cmarix.com\/qanda\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.cmarix.com\/qanda\/wp-json\/wp\/v2\/comments?post=2258"}],"version-history":[{"count":2,"href":"https:\/\/www.cmarix.com\/qanda\/wp-json\/wp\/v2\/posts\/2258\/revisions"}],"predecessor-version":[{"id":2262,"href":"https:\/\/www.cmarix.com\/qanda\/wp-json\/wp\/v2\/posts\/2258\/revisions\/2262"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.cmarix.com\/qanda\/wp-json\/wp\/v2\/media\/2259"}],"wp:attachment":[{"href":"https:\/\/www.cmarix.com\/qanda\/wp-json\/wp\/v2\/media?parent=2258"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.cmarix.com\/qanda\/wp-json\/wp\/v2\/categories?post=2258"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.cmarix.com\/qanda\/wp-json\/wp\/v2\/tags?post=2258"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}