Update CdkTestHelper to support internal constructors with BindingFlags

[ncipollina]

Summary

• Update generic CreateTestStack methods to support both public and internal constructors using BindingFlags
• Add comprehensive unit tests covering all constructor patterns
• Update documentation in README.md and CLAUDE.md
• Enable seamless testing of CDK's default internal constructor pattern

Technical Details

Enhanced Generic Methods:

• Updated CreateTestStack<TStack>() and CreateTestStack<TStack, TProps>() to use BindingFlags.NonPublic
• Uses BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic for Activator.CreateInstance
• Maintains backward compatibility with existing public constructor stacks

Why This Matters:
CDK's default pattern is internal constructors for Stack classes. Previously, the generic methods only worked with public constructors, requiring workarounds for real-world CDK stacks.

// ✅ Now works - CDK default pattern
public class MyStack : Stack
{
    internal MyStack(Construct scope, string id, IStackProps props) : base(scope, id, props) { }
}

// ✅ Still works - Custom public pattern  
public class MyStack : Stack
{
    public MyStack(Construct scope, string id, IStackProps props) : base(scope, id, props) { }
}

Test Coverage

• Added 8 new comprehensive unit tests
• Created test helper classes: TestPublicConstructorStack, TestInternalConstructorStack, TestInternalConstructorWithCustomPropsStack
• Integration tests showing end-to-end workflows with constructs
• Covers both single and dual generic method patterns

New Test Classes:

• TestPublicConstructorStack: Tests public constructor support
• TestInternalConstructorStack: Tests internal constructor support
• TestInternalConstructorWithCustomPropsStack: Tests internal constructors with custom props interfaces
• ITestInternalConstructorStackProps & TestInternalConstructorStackProps: Supporting interfaces

Documentation Updates

• README.md: Added "Supported Constructor Patterns" section with examples
• CLAUDE.md: Added comprehensive "Testing Patterns" section explaining BindingFlags usage
• Clear guidance on when and why to use internal constructor support

Benefits

• Real-World Ready: Works with CDK's default internal constructor pattern
• No Workarounds: Direct testing of custom stacks without creating unused base stacks
• Standards Compliance: Follows common testing library patterns for accessing non-public members
• Type Safety: Maintains full IntelliSense support and compile-time checks

🤖 Generated with Claude Code

[Copilot]

Pull Request Overview

Adds support for internal constructors in the CDK test helper, covers it with unit tests, and updates documentation accordingly.

• Refactored CreateTestStack methods to use BindingFlags for public and internal constructors
• Added extensive tests for public, internal, and custom‐props constructors (both full and minimal helpers)
• Expanded README and CLAUDE documentation with “Supported Constructor Patterns” and testing guidance

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
test/LayeredCraft.Cdk.Constructs.Tests/Testing/TestingHelpersTests.cs	New fact methods and helper classes to validate public/internal and custom‐props constructors
src/LayeredCraft.Cdk.Constructs/Testing/CdkTestHelper.cs	Updated CreateTestStack<TStack> and dual‐generic overload to use BindingFlags, but minimal variants were not updated
README.md	Added “Supported Constructor Patterns” section with public/internal examples
CLAUDE.md	Enhanced “Testing Patterns” to describe BindingFlags usage and dual‐generic helpers

Comments suppressed due to low confidence (1)

src/LayeredCraft.Cdk.Constructs/Testing/CdkTestHelper.cs:97

• The CreateTestStackMinimal methods were not updated to use BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, so they will fail for internal constructors. Mirroring the reflection overload from CreateTestStack into the minimal methods will ensure internal constructors are also supported.

    /// <summary>