WebApplicationFactory<T> does not default to Development environment with minimal hosting

[martincostello]

Describe the bug

Compared to the use cases for IHostBuilder and IWebHostBuilder, WebApplicationFactory<T> does not set the default environment for the application under test to Development when the code path for minimal hosting is used.

aspnetcore/src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs

Line 383 in 9a451a3

hostBuilder?.UseEnvironment(Environments.Development);

aspnetcore/src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs

Line 402 in dbf84ea

return builder.UseEnvironment(Environments.Development);

aspnetcore/src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs

Lines 152 to 178 in dbf84ea

	var hostBuilder = CreateHostBuilder();
	if (hostBuilder is not null)
	{
	ConfigureHostBuilder(hostBuilder);
	return;
	}
	var builder = CreateWebHostBuilder();
	if (builder is null)
	{
	var deferredHostBuilder = new DeferredHostBuilder();
	// This helper call does the hard work to determine if we can fallback to diagnostic source events to get the host instance
	var factory = HostFactoryResolver.ResolveHostFactory(
	typeof(TEntryPoint).Assembly,
	stopApplication: false,
	configureHostBuilder: deferredHostBuilder.ConfigureHostBuilder,
	entrypointCompleted: deferredHostBuilder.EntryPointCompleted);
	if (factory is not null)
	{
	// If we have a valid factory it means the specified entry point's assembly can potentially resolve the IHost
	// so we set the factory on the DeferredHostBuilder so we can invoke it on the call to IHostBuilder.Build.
	deferredHostBuilder.SetHostFactory(factory);
	ConfigureHostBuilder(deferredHostBuilder);
	return;
	}

Adding the missing line itself does not seem to work though, possibly related to #33876 - I've got some tests from debugging this locally I'll push up into a PR shortly see #33890.

To Reproduce

Inspect the IHostEnvironment.EnvironmentName property in, for example, the HelloWorld test.

aspnetcore/src/Mvc/test/Mvc.FunctionalTests/SimpleWithWebApplicationBuilderTests.cs

Lines 21 to 32 in 9a451a3

	[Fact]
	public async Task HelloWorld()
	{
	// Arrange
	var expected = "Hello World";
	// Act
	var content = await Client.GetStringAsync("http://localhost/");
	// Assert
	Assert.Equal(expected, content);
	}

Further technical details

• ASP.NET Core 6.0.0-preview.6.21323.4
• .NET SDK 6.0.100-preview.6.21324.1
• Visual Studio 2022 17.0.0 Preview 1.1

[ghost]

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