testing-anti-patterns

Tests must verify real behavior, not mock behavior. Mocks are a means to isolate, not the thing being tested.

Skills
Development
1

What it does and how to use it

A skill that teaches Claude Code to do development tasks well. It is packaged knowledge the model uses whenever it is relevant.

Install the skill (command above).
In Claude Code, describe what you need - the skill turns on by itself when the context fits.
No commands to memorize: you talk in plain language and the skill does the rest.

Install (Claude Code)

mkdir -p .claude/skills/testing-anti-patterns && curl -fsSL https://doutorai.pt/data/lib/skills__testing-anti-patterns.md -o .claude/skills/testing-anti-patterns/SKILL.md

Paste this command into the terminal, in your project folder, and the component installs automatically.

Content

# Testing Anti-Patterns

**Load this reference when:** writing or changing tests, adding mocks, or tempted to add test-only methods to production code.

## Overview

Tests must verify real behavior, not mock behavior. Mocks are a means to isolate, not the thing being tested.

**Core principle:** Test what the code does, not what the mocks do.

**Following strict TDD prevents these anti-patterns.**

## The Iron Laws

```
1. NEVER test mock behavior
2. NEVER add test-only methods to production classes
3. NEVER mock without understanding dependencies
```

## Anti-Pattern 1: Testing Mock Behavior


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