Functional Testing Philosophy

Core Principle

ALWAYS test the public interface of a project. Tests should interact with the system the same way end users or consumers would, never calling internal/private functions directly.

The "public interface" varies by project type:

• HTTP APIs: Test via HTTP requests to running server
• Libraries: Test via exported package functions
• CLIs: Test via command execution with captured output

CLI Testing Pattern

Code Structure

Structure CLI applications to be testable by making the main() function a thin wrapper:

package main