test-writer

name	test-writer
description	Write comprehensive tests following TDD principles Use when this capability is needed.
metadata	{"author":"etroxtaran"}

Test Writer Skill

When to Use

Use this skill when you need to:

• Write tests for new features
• Add tests for existing code (increase coverage)
• Write integration or E2E tests

Instructions

Step 1: Understand the Requirements

Read the acceptance criteria and identify:

• Happy path scenarios
• Edge cases
• Error conditions
• Integration points

Step 2: Choose Test Type

Scenario	Test Type	Framework
Single function/class	Unit test	pytest / jest
Multiple components	Integration	pytest / jest
Full user flow	E2E	Playwright
API endpoints	API test	httpx / supertest

Step 3: Write Tests

Unit Test Template (Python)

import pytest
from src.module import function_under_test

class TestFunctionName:
    """Tests for function_name."""

    def test_happy_path(self):
        """Test normal operation."""
        result = function_under_test(valid_input)
        assert result == expected_output

    def test_edge_case_empty_input(self):
        """Test with empty input."""
        result = function_under_test([])
        assert result == []

    def test_error_invalid_input(self):
        """Test error handling for invalid input."""
        with pytest.raises(ValueError, match="Invalid input"):
            function_under_test(invalid_input)

Unit Test Template (TypeScript)

import { describe, it, expect } from 'vitest';
import { functionUnderTest } from '../src/module';

describe('functionName', () => {
  it('should handle normal operation', () => {
    const result = functionUnderTest(validInput);
    expect(result).toEqual(expectedOutput);
  });

  it('should handle edge case with empty input', () => {
    const result = functionUnderTest([]);
    expect(result).toEqual([]);
  });

  it('should throw error for invalid input', () => {
    expect(() => functionUnderTest(invalidInput)).toThrow('Invalid input');
  });
});

Step 4: Run and Verify Failure

# Python
pytest tests/test_new_feature.py -v

# TypeScript
npm test -- tests/new-feature.test.ts

Tests MUST fail before implementation.

Step 5: Report

{
  "status": "tests_written",
  "tests_count": 5,
  "test_file": "tests/test_feature.py",
  "ready_for_implementation": true
}

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