Testing Patterns Skill

Status: Active Last Updated: 2026-01-08

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Overview

This skill provides testing patterns and requirements for Claude Family projects.

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RECOMMENDED: Spawn Tester Agent

Per the Delegation Rules, consider spawning tester-haiku for test writing:

# Spawn tester agent to write tests for new code
mcp__orchestrator__spawn_agent(
    agent_type="tester-haiku",
    task="Write unit tests for the new functions in src/feature.ts. Cover happy path, edge cases, and error scenarios.",
    workspace_dir="C:/Projects/current-project"
)

# For E2E web tests, use web-tester-haiku
mcp__orchestrator__spawn_agent(
    agent_type="web-tester-haiku",
    task="Write Playwright E2E tests for the login flow.",
    workspace_dir="C:/Projects/current-project"
)

Test writing is structured work - Haiku agents handle it well and cheaply.

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Quick Reference

Test Levels

Level	Purpose	When to Run
Unit	Individual function/class	Every change
Integration	Component interactions	Before commit
Regression	Full feature coverage	Before release
Smoke	Critical paths only	After deploy

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Python Testing

Framework: pytest

# Run all tests
pytest tests/

# Run specific test file
pytest tests/test_feature.py

# Run with verbose output
pytest -v

# Run with coverage
pytest --cov=src tests/

Test Structure

# tests/test_feature.py
import pytest

class TestFeature:
    def setup_method(self):
        """Run before each test method"""
        pass
    
    def test_happy_path(self):
        """Test normal operation"""
        result = function_under_test(valid_input)
        assert result == expected_output
    
    def test_edge_case(self):
        """Test boundary conditions"""
        pass
    
    def test_error_handling(self):
        """Test error scenarios"""
        with pytest.raises(ValueError):
            function_under_test(invalid_input)

Fixtures

@pytest.fixture
def db_connection():
    """Provide test database connection"""
    conn = create_test_connection()
    yield conn
    conn.close()

def test_database_query(db_connection):
    result = db_connection.execute("SELECT 1")
    assert result is not None

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TypeScript Testing

Framework: Jest or Vitest

# Jest
npm test

# Vitest
npx vitest

Test Structure

import { describe, it, expect, beforeEach } from 'vitest';

describe('Feature', () => {
  beforeEach(() => {
    // Setup
  });
  
  it('should handle normal input', () => {
    const result = functionUnderTest(validInput);
    expect(result).toBe(expectedOutput);
  });
  
  it('should throw on invalid input', () => {
    expect(() => functionUnderTest(invalidInput)).toThrow();
  });
});

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Regression Testing

Claude Family Pattern

# scripts/run_regression_tests.py
def run_test(test_case):
    """Run single test case and return pass/fail"""
    try:
        result = execute_test(test_case)
        return result.success, result.message
    except Exception as e:
        return False, str(e)

def run_all_tests():
    """Run all regression tests"""
    results = []
    for test in TEST_CASES:
        passed, message = run_test(test)
        results.append((test.name, passed, message))
    return results

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Database Testing

Test Database Pattern

@pytest.fixture(scope="session")
def test_db():
    """Create isolated test database"""
    # Create test schema
    conn = get_connection()
    conn.execute("CREATE SCHEMA IF NOT EXISTS test_claude")
    
    yield conn
    
    # Cleanup
    conn.execute("DROP SCHEMA test_claude CASCADE")

Data Validation Testing

def test_column_registry_enforcement():
    """Verify column constraints are enforced"""
    with pytest.raises(psycopg.errors.CheckViolation):
        insert_invalid_status_value()

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Key Gotchas

1. Generic Constraints for Data Hooks

// WRONG: TypeScript interfaces fail Record constraint
function useTableSort<T extends Record<string, unknown>>(data: T[]) {}

// CORRECT: Use broader object constraint
function useTableSort<T extends object>(data: T[]) {}

2. Test Isolation

Always clean up after tests. Use transactions that rollback:

@pytest.fixture
def db_transaction(db_connection):
    with db_connection.transaction() as tx:
        yield tx
        tx.rollback()  # Always rollback

3. Async Testing

@pytest.mark.asyncio
async def test_async_function():
    result = await async_function()
    assert result is not None

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Pre-Commit Checklist

Before committing code:

• All unit tests pass
• Integration tests pass
• No new lint warnings
• Coverage not decreased
• Edge cases covered

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Related Skills

• database-operations - Database testing specifics
• code-review - Review process includes test verification

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Version: 1.1 (Added agent spawning guidance) Created: 2025-12-26 Updated: 2026-01-10 Location: .claude/skills/testing/skill.md