Struggling to Mock a Complex Configuration Object in ASP.NET Unit Tests
I've been banging my head against this for hours. I'm trying to unit test a method in my ASP.NET Core application that takes a complex configuration object as a dependency. This configuration object is initialized in the `Startup.cs` file and contains nested properties that are essential for my method to function properly. However, when I attempt to mock this configuration using Moq, I end up with an `ArgumentNullException` because certain properties are still null. Here’s a simplified version of my setup: ```csharp public class MyService { private readonly MyConfig _config; public MyService(MyConfig config) { _config = config ?? throw new ArgumentNullException(nameof(config)); } public int Calculate() { return _config.NestedProperty.Value * 2; } } public class MyConfig { public NestedConfig NestedProperty { get; set; } } public class NestedConfig { public int Value { get; set; } } ``` In my unit test, I try to mock the `MyConfig` object like this: ```csharp var mockConfig = new Mock<MyConfig>(); var nestedMock = new Mock<NestedConfig>(); mockConfig.SetupGet(c => c.NestedProperty).Returns(nestedMock.Object); nestedMock.SetupGet(n => n.Value).Returns(5); var service = new MyService(mockConfig.Object); var result = service.Calculate(); ``` However, I receive the behavior `System.ArgumentNullException: Value want to be null. (Parameter 'config')` because `mockConfig.Object` returns a `MyConfig` instance with a null `NestedProperty`. I’ve tried various ways to set up the mock, but I need to seem to get it to work properly. How can I effectively mock this configuration object to ensure that all necessary properties are initialized correctly for my unit tests? My development environment is Linux. Has anyone else encountered this?