ASP.NET Core Integration Tests - Breaking change in .NET Core 3.0

 Yesterday I blogged about how to get started with integration testing in ASP.NET Core.

If you are using this technique, you might get a few issues while migrating from .NET Core 2.2 to .NET Core 3.0 or 3.1.

It could be that you get the following error message:

No method 'public static IHostBuilder CreateHostBuilder(string[] args)' or 'public static IWebHostBuilder CreateWebHostBuilder(string[] args)' found on 'AutoGeneratedProgram'. Alternatively, WebApplicationFactory`1 can be extended and 'CreateHostBuilder' or 'CreateWebHostBuilder' can be overridden to provide your own instance.

This is due to the switch from the WebHostBuilder to the more generic HostBuilder in .NET Core 3.x. 

You should use the CreateHostBuilder() method. It is still possible to access the WebHostBuilder through the ConfigureWebHostDefault() method:

	public sealed class SelfHostedApi : WebApplicationFactory<Api.Startup>
	{
	protected override IHostBuilder CreateHostBuilder()
	{
	return Host.CreateDefaultBuilder().ConfigureWebHostDefaults(builder =>
	builder.UseStartup<Api.Startup>());
	}
	protected override void ConfigureWebHost(IWebHostBuilder builder)
	{
	builder.ConfigureServices(services =>
	{
	});
	}
	}

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