What are the four layers of validation used in this pattern?

The pattern utilizes Entry Point Validation, Business Logic Validation, Environment Guards, and Debug Instrumentation to catch errors at different stages.

Why is one validation check not enough?

A single check can be bypassed by different code paths, refactoring, or test mocks. Multiple layers ensure that if one check is skipped, others will still catch the error.

What is the core principle of this Defense-in-Depth skill?

The core principle is to validate data at every single layer it passes through, making it structurally impossible for invalid data to cause deep execution failures.

How do environment guards help during testing?

Environment guards prevent dangerous operations, such as initializing a Git repository in a source directory, by checking if the process is running in a test context and restricting actions to temporary directories.

Defense-in-Depth Validation

Name: Defense-in-Depth Validation
Author: keenanthomson

bykeenanthomson

Security & Testing

Enforces a multi-layered validation strategy across application layers to make structural bugs impossible and ensure data integrity.

About

The Defense-in-Depth skill provides a systematic framework for hardening software by implementing redundant, multi-layer validation. Rather than relying on a single check that could be bypassed by refactoring or mocks, this pattern guides you to validate data at the entry point, within business logic, through environment guards, and via debug instrumentation. This approach is essential for complex systems where data integrity is paramount, ensuring that invalid states are caught regardless of the code path taken or the execution context.

Key Features

Structured patterns to eliminate entire classes of bugs
Environment guards to prevent dangerous operations in specific contexts
Logic-level validation for internal business consistency
0 GitHub stars
Debug instrumentation for enhanced forensic analysis
Entry point validation for API and boundary protection

Use Cases

Hardening critical file system operations against invalid pathing
Preventing destructive commands from running outside of safe test environments
Securing business logic against bypasses during refactoring or mocking

About

Key Features

Structured patterns to eliminate entire classes of bugs
Environment guards to prevent dangerous operations in specific contexts
Logic-level validation for internal business consistency
0 GitHub stars
Debug instrumentation for enhanced forensic analysis
Entry point validation for API and boundary protection

Use Cases

Hardening critical file system operations against invalid pathing
Preventing destructive commands from running outside of safe test environments
Securing business logic against bypasses during refactoring or mocking