Unit and Integration Testing In ASP.NET Core Applications

It is a popular and versatile framework for building web applications. Tests that verify your application’s behavior are crucial to ensuring its correct functionality. Unit tests and integration tests are two types of tests you can write for ASP.NET Core applications.

While unit tests test individual pieces of code, integration tests test the interactions between different parts of the application. In order to verify the behavior and quality of an ASP.NET Core application, both types of tests are essential. The purpose of this article is to explain what unit tests and integration tests are, why they’re important, and how to write them for ASP.NET Core applications.

Understanding Unit Tests

Testing ASP.NET Core Applications

A unit test verifies the behavior of an individual function, method, or class. These tests test small, isolated pieces of code without considering their interactions with other parts of the application. Tests should be fast, repeatable, and easy to write. It is also important that they are independent of any external dependencies, such as databases or APIs.

Unit tests play an important role in the development process since they help you make sure your code behaves as you intended. Unit tests can help you catch bugs early in the development process before they become larger and more difficult to fix. As a safety net, unit tests also make refactoring your code easier, as they ensure that changes don’t break existing functionality.

In order to write unit tests for ASP.NET Core applications, you’ll need a testing framework. Several testing frameworks are available for .NET, including MSTest and xUnit. The frameworks provide the tools you need to write, run, and manage your tests.

The following is an example of an MSTest unit test that tests a simple function that calculates the sum of two numbers:

public class UnitTests
    public void TestSum()
        int a = 5;
        int b = 10;
        int expected = 15;
        int result = Sum(a, b);
        Assert.AreEqual(expected, result);

    int Sum(int a, int b)
        return a + b;

This example specifies that this is a unit test class and method using the TestClass and TestMethod attributes. In the TestSum method, the Sum function is tested by calling it with two arguments and checking whether the result matches the expected one.

Understanding Integration Tests

Integration tests focus on the interactions between different parts of an application. They ensure that the application behaves correctly when all its components are working together. Tests of integration are slower and more complex than unit tests, but they provide a more comprehensive understanding of the application’s behavior.

Performing integration tests ensures that your application works as expected, even when all its components are working together. They help you detect bugs and problems that may not be obvious from unit tests alone. Your application’s integration with external dependencies, such as databases or APIs, is also validated by integration tests.

An ASP.NET Core application can be tested with a testing framework like TestServer or Selenium. You can run the application in a test environment, interact with it as a user would, and verify that it behaves as expected.

The following integration test in TestServer tests a simple API endpoint that returns a list of values:

public async Task TestGetValues()
    var server = new TestServer(new WebHostBuilder().UseStartup<Startup>());
    var client = server.CreateClient();

    var response = await client.GetAsync("/api/values");

    var values = JsonConvert.DeserializeObject<List<string>>(await response.Content.ReadAsStringAsync());
    Assert.Equal(2, values.Count);
    Assert.Contains("value1", values);
    Assert.Contains("value2", values);

The Fact attribute specifies that this is an integration test method. TestGetValues creates a TestServer instance to run the application and makes a request to the API endpoint using a HttpClient. Afterward, the test verifies that the response from the endpoint is a successful HTTP response and that the returned JSON content is a list of values.


In order to ensure the quality and reliability of an ASP.NET Core application, both unit tests and integration tests are essential. While unit tests focus on individual pieces of code, integration tests focus on how the different parts of the application interact. Your development process should include both types of tests for verifying your application’s behavior and functionality. Following the techniques outlined in this article, you can write and run effective unit tests and integration tests for your ASP.NET Core application.

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