Integration tests in ASP.NET Core

By Luke Latham and Steve Smith

Integration tests ensure that an app's components function correctly at a level that includes the app's supporting infrastructure, such as the database, file system, and network. ASP.NET Core supports integration tests using a unit test framework with a test web host and an in-memory test server.

This topic assumes a basic understanding of unit tests. If unfamiliar with test concepts, see the Unit Testing in .NET Core and .NET Standard topic and its linked content.

View or download sample code (how to download)

The sample app is a Razor Pages app and assumes a basic understanding of Razor Pages. If unfamiliar with Razor Pages, see the following topics:

Introduction to integration tests

Integration tests evaluate an app's components on a broader level than unit tests. Unit tests are used to test isolated software components, such as individual class methods. Integration tests confirm that two or more app components work together to produce an expected result, possibly including every component required to fully process a request.

These broader tests are used to test the app's infrastructure and whole framework, often including the following components:

  • Database
  • File system
  • Network appliances
  • Request-response pipeline

Unit tests use fabricated components, known as fakes or mock objects, in place of infrastructure components.

In contrast to unit tests, integration tests:

  • Use the actual components that the app uses in production.
  • Require more code and data processing.
  • Take longer to run.

Therefore, limit the use of integration tests to the most important infrastructure scenarios. If a behavior can be tested using either a unit test or an integration test, choose the unit test.

Tip

Don't write integration tests for every possible permutation of data and file access with databases and file systems. Regardless of how many places across an app interact with databases and file systems, a focused set of read, write, update, and delete integration tests are usually capable of adequately testing database and file system components. Use unit tests for routine tests of method logic that interact with these components. In unit tests, the use of infrastructure fakes/mocks result in faster test execution.

Note

In discussions of integration tests, the tested project is frequently called the system under test, or "SUT" for short.

ASP.NET Core integration tests

Integration tests in ASP.NET Core require the following:

  • A test project is used to contain and execute the tests. The test project has a reference to the tested ASP.NET Core project, called the system under test (SUT). "SUT" is used throughout this topic to refer to the tested app.
  • The test project creates a test web host for the SUT and uses a test server client to handle requests and responses to the SUT.
  • A test runner is used to execute the tests and report the test results.

Integration tests follow a sequence of events that include the usual Arrange, Act, and Assert test steps:

  1. The SUT's web host is configured.
  2. A test server client is created to submit requests to the app.
  3. The Arrange test step is executed: The test app prepares a request.
  4. The Act test step is executed: The client submits the request and receives the response.
  5. The Assert test step is executed: The actual response is validated as a pass or fail based on an expected response.
  6. The process continues until all of the tests are executed.
  7. The test results are reported.

Usually, the test web host is configured differently than the app's normal web host for the test runs. For example, a different database or different app settings might be used for the tests.

Infrastructure components, such as the test web host and in-memory test server (TestServer), are provided or managed by the Microsoft.AspNetCore.Mvc.Testing package. Use of this package streamlines test creation and execution.

The Microsoft.AspNetCore.Mvc.Testing package handles the following tasks:

  • Copies the dependencies file (*.deps) from the SUT into the test project's bin folder.
  • Sets the content root to the SUT's project root so that static files and pages/views are found when the tests are executed.
  • Provides the WebApplicationFactory class to streamline bootstrapping the SUT with TestServer.

The unit tests documentation describes how to set up a test project and test runner, along with detailed instructions on how to run tests and recommendations for how to name tests and test classes.

Note

When creating a test project for an app, separate the unit tests from the integration tests into different projects. This helps ensure that infrastructure testing components aren't accidently included in the unit tests. Separation of unit and integration tests also allows control over which set of tests are run.

There's virtually no difference between the configuration for tests of Razor Pages apps and MVC apps. The only difference is in how the tests are named. In a Razor Pages app, tests of page endpoints are usually named after the page model class (for example, IndexPageTests to test component integration for the Index page). In an MVC app, tests are usually organized by controller classes and named after the controllers they test (for example, HomeControllerTests to test component integration for the Home controller).

Test app prerequisites

The test project must:

  • Have a package reference for Microsoft.AspNetCore.App.
  • Use the Web SDK in the project file (<Project Sdk="Microsoft.NET.Sdk.Web">).

These prerequesities can be seen in the sample app. Inspect the tests/RazorPagesProject.Tests/RazorPagesProject.Tests.csproj file.

Basic tests with the default WebApplicationFactory

WebApplicationFactory<TEntryPoint> is used to create a TestServer for the integration tests. TEntryPoint is the entry point class of the SUT, usually the Startup class.

Test classes implement a class fixture interface (IClassFixture) to indicate the class contains tests and provide shared object instances across the tests in the class.

Basic test of app endpoints

The following test class, BasicTests, uses the WebApplicationFactory to bootstrap the SUT and provide an HttpClient to a test method, Get_EndpointsReturnSuccessAndCorrectContentType. The method checks if the response status code is successful (status codes in the range 200-299) and the Content-Type header is text/html; charset=utf-8 for several app pages.

CreateClient creates an instance of HttpClient that automatically follows redirects and handles cookies.

public class BasicTests 
    : IClassFixture<WebApplicationFactory<RazorPagesProject.Startup>>
{
    private readonly WebApplicationFactory<RazorPagesProject.Startup> _factory;

    public BasicTests(WebApplicationFactory<RazorPagesProject.Startup> factory)
    {
        _factory = factory;
    }

    [Theory]
    [InlineData("/")]
    [InlineData("/Index")]
    [InlineData("/About")]
    [InlineData("/Privacy")]
    [InlineData("/Contact")]
    public async Task Get_EndpointsReturnSuccessAndCorrectContentType(string url)
    {
        // Arrange
        var client = _factory.CreateClient();

        // Act
        var response = await client.GetAsync(url);

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

Test a secure endpoint

Another test in the BasicTests class checks that a secure endpoint redirects an unauthenticated user to the app's Login page.

In the SUT, the /SecurePage page uses an AuthorizePage convention to apply an AuthorizeFilter to the page. For more information, see Razor Pages authorization conventions.

services.AddMvc()
    .SetCompatibilityVersion(CompatibilityVersion.Version_2_1)
    .AddRazorPagesOptions(options =>
    {
        options.Conventions.AuthorizePage("/SecurePage");
    });

In the Get_SecurePageRequiresAnAuthenticatedUser test, a WebApplicationFactoryClientOptions is set to disallow redirects by setting AllowAutoRedirect to false:

[Fact]
public async Task Get_SecurePageRequiresAnAuthenticatedUser()
{
    // Arrange
    var client = _factory.CreateClient(
        new WebApplicationFactoryClientOptions
        {
            AllowAutoRedirect = false
        });

    // Act
    var response = await client.GetAsync("/SecurePage");

    // Assert
    Assert.Equal(HttpStatusCode.Redirect, response.StatusCode);
    Assert.StartsWith("http://localhost/Identity/Account/Login", 
        response.Headers.Location.OriginalString);
}

By disallowing the client to follow the redirect, the following checks can be made:

  • The status code returned by the SUT can be checked against the expected HttpStatusCode.Redirect result, not the final status code after the redirect to the Login page, which would be HttpStatusCode.OK.
  • The Location header value in the response headers is checked to confirm that it starts with http://localhost/Identity/Account/Login, not the final Login page response, where the Location header wouldn't be present.

For more information on WebApplicationFactoryClientOptions, see the Client options section.

Customize WebApplicationFactory

Web host configuration can be created independently of the test classes by inheriting from WebApplicationFactory to create one or more custom factories:

  1. Inherit from WebApplicationFactory and override ConfigureWebHost. The IWebHostBuilder allows the configuration of the service collection with ConfigureServices:

    public class CustomWebApplicationFactory<TStartup> 
        : WebApplicationFactory<RazorPagesProject.Startup>
    {
        protected override void ConfigureWebHost(IWebHostBuilder builder)
        {
            builder.ConfigureServices(services =>
            {
                // Create a new service provider.
                var serviceProvider = new ServiceCollection()
                    .AddEntityFrameworkInMemoryDatabase()
                    .BuildServiceProvider();
    
                // Add a database context (ApplicationDbContext) using an in-memory 
                // database for testing.
                services.AddDbContext<ApplicationDbContext>(options => 
                {
                    options.UseInMemoryDatabase("InMemoryDbForTesting");
                    options.UseInternalServiceProvider(serviceProvider);
                });
    
                // Build the service provider.
                var sp = services.BuildServiceProvider();
    
                // Create a scope to obtain a reference to the database
                // context (ApplicationDbContext).
                using (var scope = sp.CreateScope())
                {
                    var scopedServices = scope.ServiceProvider;
                    var db = scopedServices.GetRequiredService<ApplicationDbContext>();
                    var logger = scopedServices
                        .GetRequiredService<ILogger<CustomWebApplicationFactory<TStartup>>>();
    
                    // Ensure the database is created.
                    db.Database.EnsureCreated();
    
                    try
                    {
                        // Seed the database with test data.
                        Utilities.InitializeDbForTests(db);
                    }
                    catch (Exception ex)
                    {
                        logger.LogError(ex, $"An error occurred seeding the " +
                            "database with test messages. Error: {ex.Message}");
                    }
                }
            });
        }
    }
    

    Database seeding in the sample app is performed by the InitializeDbForTests method. The method is described in the Integration tests sample: Test app organization section.

  2. Use the custom CustomWebApplicationFactory in test classes. The following example uses the factory in the IndexPageTests class:

    public class IndexPageTests : IClassFixture<CustomWebApplicationFactory<RazorPagesProject.Startup>>
    {
        private readonly HttpClient _client;
        private readonly CustomWebApplicationFactory<RazorPagesProject.Startup> _factory;
    
        public IndexPageTests(
            CustomWebApplicationFactory<RazorPagesProject.Startup> factory)
        {
            _client = factory.CreateClient(new WebApplicationFactoryClientOptions
                {
                    AllowAutoRedirect = false
                });
            _factory = factory;
        }
    

    The sample app's client is configured to prevent the HttpClient from following redirects. As explained in the Test a secure endpoint section, this permits tests to check the result of the app's first response. The first response is a redirect in many of these tests with a Location header.

  3. A typical test uses the HttpClient and helper methods to process the request and the response:

    [Fact]
    public async Task Post_DeleteAllMessagesHandler_ReturnsRedirectToRoot()
    {
        // Arrange
        var defaultPage = await _client.GetAsync("/");
        var content = await HtmlHelpers.GetDocumentAsync(defaultPage);
    
        //Act
        var response = await _client.SendAsync(
            (IHtmlFormElement)content.QuerySelector("form[id='messages']"),
            (IHtmlButtonElement)content.QuerySelector("button[id='deleteAllBtn']"));
    
        // Assert
        Assert.Equal(HttpStatusCode.OK, defaultPage.StatusCode);
        Assert.Equal(HttpStatusCode.Redirect, response.StatusCode);
        Assert.Equal("/", response.Headers.Location.OriginalString);
    }
    

Any POST request to the SUT must satisfy the antiforgery check that's automatically made by the app's data protection antiforgery system. In order to arrange for a test's POST request, the test app must:

  1. Make a request for the page.
  2. Parse the antiforgery cookie and request validation token from the response.
  3. Make the POST request with the antiforgery cookie and request validation token in place.

The SendAsync helper extension methods (Helpers/HttpClientExtensions.cs) and the GetDocumentAsync helper method (Helpers/HtmlHelpers.cs) in the sample app use the AngleSharp parser to handle the antiforgery check with the following methods:

  • GetDocumentAsync – Receives the HttpResponseMessage and returns an IHtmlDocument. GetDocumentAsync uses a factory that prepares a virtual response based on the original HttpResponseMessage. For more information, see the AngleSharp documentation.
  • SendAsync extension methods for the HttpClient compose an HttpRequestMessage and call SendAsync(HttpRequestMessage) to submit requests to the SUT. Overloads for SendAsync accept the HTML form (IHtmlFormElement) and the following:
    • Submit button of the form (IHtmlElement)
    • Form values collection (IEnumerable<KeyValuePair<string, string>>)
    • Submit button (IHtmlElement) and form values (IEnumerable<KeyValuePair<string, string>>)

Note

AngleSharp is a third-party parsing library used for demonstration purposes in this topic and the sample app. AngleSharp isn't supported or required for integration testing of ASP.NET Core apps. Other parsers can be used, such as the Html Agility Pack (HAP). Another approach is to write code to handle the antiforgery system's request verification token and antiforgery cookie directly.

Customize the client with WithWebHostBuilder

When additional configuration is required within a test method, WithWebHostBuilder creates a new WebApplicationFactory with an IWebHostBuilder that is further customized by configuration.

The Post_DeleteMessageHandler_ReturnsRedirectToRoot test method of the sample app demonstrates the use of WithWebHostBuilder. This test performs a record delete in the database by triggering a form submission in the SUT.

Because another test in the IndexPageTests class performs an operation that deletes all of the records in the database and may run before the Post_DeleteMessageHandler_ReturnsRedirectToRoot method, the database is seeded in this test method to ensure that a record is present for the SUT to delete. Selecting the deleteBtn1 button of the messages form in the SUT is simulated in the request to the SUT:

[Fact]
public async Task Post_DeleteMessageHandler_ReturnsRedirectToRoot()
{
    // Arrange
    var client = _factory.WithWebHostBuilder(builder =>
        {
            builder.ConfigureServices(services =>
            {
                var serviceProvider = services.BuildServiceProvider();

                using (var scope = serviceProvider.CreateScope())
                {
                    var scopedServices = scope.ServiceProvider;
                    var db = scopedServices
                        .GetRequiredService<ApplicationDbContext>();
                    var logger = scopedServices
                        .GetRequiredService<ILogger<IndexPageTests>>();

                    try
                    {
                        Utilities.InitializeDbForTests(db);
                    }
                    catch (Exception ex)
                    {
                        logger.LogError(ex, "An error occurred seeding " +
                            "the database with test messages. Error: " +
                            ex.Message);
                    }
                }
            });
        })
        .CreateClient(new WebApplicationFactoryClientOptions
            {
                AllowAutoRedirect = false
            });
    var defaultPage = await client.GetAsync("/");
    var content = await HtmlHelpers.GetDocumentAsync(defaultPage);

    //Act
    var response = await client.SendAsync(
        (IHtmlFormElement)content.QuerySelector("form[id='messages']"),
        (IHtmlButtonElement)content.QuerySelector("button[id='deleteBtn1']"));

    // Assert
    Assert.Equal(HttpStatusCode.OK, defaultPage.StatusCode);
    Assert.Equal(HttpStatusCode.Redirect, response.StatusCode);
    Assert.Equal("/", response.Headers.Location.OriginalString);
}

Client options

The following table shows the default WebApplicationFactoryClientOptions available when creating HttpClient instances.

Option Description Default
AllowAutoRedirect Gets or sets whether or not HttpClient instances should automatically follow redirect responses. true
BaseAddress Gets or sets the base address of HttpClient instances. http://localhost
HandleCookies Gets or sets whether HttpClient instances should handle cookies. true
MaxAutomaticRedirections Gets or sets the maximum number of redirect responses that HttpClient instances should follow. 7

Create the WebApplicationFactoryClientOptions class and pass it to the CreateClient method (default values are shown in the code example):

// Default client option values are shown
var clientOptions = new WebApplicationFactoryClientOptions();
clientOptions.AllowAutoRedirect = true;
clientOptions.BaseAddress = new Uri("http://localhost");
clientOptions.HandleCookies = true;
clientOptions.MaxAutomaticRedirections = 7;

_client = _factory.CreateClient(clientOptions);

How the test infrastructure infers the app content root path

The WebApplicationFactory constructor infers the app content root path by searching for a WebApplicationFactoryContentRootAttribute on the assembly containing the integration tests with a key equal to the TEntryPoint assembly System.Reflection.Assembly.FullName. In case an attribute with the correct key isn't found, WebApplicationFactory falls back to searching for a solution file (*.sln) and appends the TEntryPoint assembly name to the solution directory. The app root directory (the content root path) is used to discover views and content files.

In most cases, it isn't necessary to explicitly set the app content root, as the search logic usually finds the correct content root at runtime. In special scenarios where the content root isn't found using the built-in search algorithm, the app content root can be specified explicitly or by using custom logic. To set the app content root in those scenarios, call the UseSolutionRelativeContentRoot extension method from the Microsoft.AspNetCore.TestHost package. Supply the solution's relative path and optional solution file name or glob pattern (default = *.sln).

Call the UseSolutionRelativeContentRoot extension method using ONE of the following approaches:

  • When configuring test classes with WebApplicationFactory, provide a custom configuration with the IWebHostBuilder:

    public IndexPageTests(
         WebApplicationFactory<RazorPagesProject.Startup> factory)
    {
         var _factory = factory.WithWebHostBuilder(builder =>
         {
             builder.UseSolutionRelativeContentRoot("<SOLUTION-RELATIVE-PATH>");
    
             ...
         });
    }
    
  • When configuring test classes with a custom WebApplicationFactory, inherit from WebApplicationFactory and override ConfigureWebHost:

    public class CustomWebApplicationFactory<TStartup>
         : WebApplicationFactory<RazorPagesProject.Startup>
    {
         protected override void ConfigureWebHost(IWebHostBuilder builder)
         {
             builder.ConfigureServices(services =>
             {
                 builder.UseSolutionRelativeContentRoot("<SOLUTION-RELATIVE-PATH>");
    
                 ...
             });
         }
    }
    

Disable shadow copying

Shadow copying causes the tests to execute in a different folder than the output folder. For tests to work properly, shadow copying must be disabled. The sample app uses xUnit and disables shadow copying for xUnit by including an xunit.runner.json file with the correct configuration setting. For more information, see Configuring xUnit.net with JSON.

Add the xunit.runner.json file to root of the test project with the following content:

{
  "shadowCopy": false
}

Integration tests sample

The sample app is composed of two apps:

App Project folder Description
Message app (the SUT) src/RazorPagesProject Allows a user to add, delete one, delete all, and analyze messages.
Test app tests/RazorPagesProject.Tests Used to integration test the SUT.

The tests can be run using the built-in test features of an IDE, such as Visual Studio. If using Visual Studio Code or the command line, execute the following command at a command prompt in the tests/RazorPagesProject.Tests folder:

dotnet test

Message app (SUT) organization

The SUT is a Razor Pages message system with the following characteristics:

  • The Index page of the app (Pages/Index.cshtml and Pages/Index.cshtml.cs) provides a UI and page model methods to control the addition, deletion, and analysis of messages (average words per message).
  • A message is described by the Message class (Data/Message.cs) with two properties: Id (key) and Text (message). The Text property is required and limited to 200 characters.
  • Messages are stored using Entity Framework's in-memory database†.
  • The app contains a data access layer (DAL) in its database context class, AppDbContext (Data/AppDbContext.cs).
  • If the database is empty on app startup, the message store is initialized with three messages.
  • The app includes a /SecurePage that can only be accessed by an authenticated user.

†The EF topic, Test with InMemory, explains how to use an in-memory database for tests with MSTest. This topic uses the xUnit test framework. Test concepts and test implementations across different test frameworks are similar but not identical.

Although the app doesn't use the repository pattern and isn't an effective example of the Unit of Work (UoW) pattern, Razor Pages supports these patterns of development. For more information, see Designing the infrastructure persistence layer, Implementing the Repository and Unit of Work Patterns in an ASP.NET MVC Application, and Test controller logic (the sample implements the repository pattern).

Test app organization

The test app is a console app inside the tests/RazorPagesProject.Tests folder.

Test app folder Description
BasicTests BasicTests.cs contains test methods for routing, accessing a secure page by an unauthenticated user, and obtaining a GitHub user profile and checking the profile's user login.
IntegrationTests IndexPageTests.cs contains the integration tests for the Index page using custom WebApplicationFactory class.
Helpers/Utilities
  • Utilities.cs contains the InitializeDbForTests method used to seed the database with test data.
  • HtmlHelpers.cs provides a method to return an AngleSharp IHtmlDocument for use by the test methods.
  • HttpClientExtensions.cs provide overloads for SendAsync to submit requests to the SUT.

The test framework is xUnit. Integration tests are conducted using the Microsoft.AspNetCore.TestHost, which includes the TestServer. Because the Microsoft.AspNetCore.Mvc.Testing package is used to configure the test host and test server, the TestHost and TestServer packages don't require direct package references in the test app's project file or developer configuration in the test app.

Seeding the database for testing

Integration tests usually require a small dataset in the database prior to the test execution. For example, a delete test calls for a database record deletion, so the database must have at least one record for the delete request to succeed.

The sample app seeds the database with three messages in Utilities.cs that tests can use when they execute:

public static void InitializeDbForTests(ApplicationDbContext db)
{
    db.Messages.AddRange(GetSeedingMessages());
    db.SaveChanges();
}

public static List<Message> GetSeedingMessages()
{
    return new List<Message>()
    {
        new Message(){ Text = "TEST RECORD: You're standing on my scarf." },
        new Message(){ Text = "TEST RECORD: Would you like a jelly baby?" },
        new Message(){ Text = "TEST RECORD: To the rational mind, " +
            "nothing is inexplicable; only unexplained." }
    };
}

Additional resources