Custom AppSettings Configuration in ASP.NET Core Tests

Aug 10, 2023
•
2 min read
•
.NET Core •
Testing

Problem: The ASP.NET integration tests use the web application project appsettings.json configuration. When you start the web application from the integration tests using the TestServer (from the Microsoft.AspNetCore.Mvc.Testing package), the web application uses the appsettings.json configuration files that are placed in the web application root directory. Normally this doesn't suit us well since we need to have different configs for our integration tests for things like connection strings, storage URLs, etc.

Solution: Configure the ASP.NET integration tests to use the test project specific appsettings.json configuration.

To do this, create appsettings.json and appsettings.Development.json configuration files in the integration tests project.

Then, set the properties Build Action = Content and Copy to output directory = Copy if newer to both files.

Finally, configure the WebApplicationFactory to use the configuration files from the test project itself. Here is a sample code and a test case.

using Microsoft.AspNetCore.Mvc.Testing;
using Microsoft.Extensions.Configuration;

namespace PlaygroundApi.Tests
{
    public class UnitTest1
    {
        private readonly WebApplicationFactory<PlaygroundApi.Program> _webAppFactory;

        public UnitTest1()
        {
            _webAppFactory = new WebApplicationFactory<PlaygroundApi.Program>()
                .WithWebHostBuilder(builder =>
                {
                    builder.ConfigureAppConfiguration((context, config) =>
                    {
                        // Set the base path to the integration tests build output directory
                        // where the integration tests' config files will be copied into.
                        config.SetBasePath(Directory.GetCurrentDirectory());
                        config.AddJsonFile("appsettings.json");
                        config.AddJsonFile("appsettings.Development.json");
                    });
                });
        }

        [Fact]
        public async Task Test1()
        {
            var httpClient = _webAppFactory.CreateClient();

            var result = await httpClient.GetStringAsync("/");

            // Here the endpoint returns configuration specific result for testing purposes.
            Assert.Equal("ProjectKey is: 'integrationtests_local_development'", result);
        }
    }
}