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TDD Guide

A step-by-step guide and live coding partner for test-driven development — write failing tests first, then implement just enough code to pass.

Built for: Developers

What this skill does

Build more reliable software by writing tests before implementing features, ensuring every function works as expected from the start. Instantly generate test cases and identify exactly where your project needs better coverage to prevent bugs. Reach for this assistant whenever you want to validate new logic, improve quality, or avoid writing every test from scratch.

@alirezarezvani · Development
view on github ↗

name: “tdd-guide” description: “Test-driven development skill for writing unit tests, generating test fixtures and mocks, analyzing coverage gaps, and guiding red-green-refactor workflows across Jest, Pytest, JUnit, Vitest, and Mocha. Use when the user asks to write tests, improve test coverage, practice TDD, generate mocks or stubs, or mentions testing frameworks like Jest, pytest, or JUnit. Handles test generation from source code, coverage report parsing (LCOV/JSON/XML), quality scoring, and framework conversion for TypeScript, JavaScript, Python, and Java projects.” triggers:

  • generate tests
  • analyze coverage
  • TDD workflow
  • red green refactor
  • Jest tests
  • Pytest tests
  • JUnit tests
  • coverage report

TDD Guide

Test-driven development skill for generating tests, analyzing coverage, and guiding red-green-refactor workflows across Jest, Pytest, JUnit, and Vitest.


Workflows

Generate Tests from Code

  1. Provide source code (TypeScript, JavaScript, Python, Java)
  2. Specify target framework (Jest, Pytest, JUnit, Vitest)
  3. Run test_generator.py with requirements
  4. Review generated test stubs
  5. Validation: Tests compile and cover happy path, error cases, edge cases

Analyze Coverage Gaps

  1. Generate coverage report from test runner (npm test -- --coverage)
  2. Run coverage_analyzer.py on LCOV/JSON/XML report
  3. Review prioritized gaps (P0/P1/P2)
  4. Generate missing tests for uncovered paths
  5. Validation: Coverage meets target threshold (typically 80%+)

TDD New Feature

  1. Write failing test first (RED)
  2. Run tdd_workflow.py --phase red to validate
  3. Implement minimal code to pass (GREEN)
  4. Run tdd_workflow.py --phase green to validate
  5. Refactor while keeping tests green (REFACTOR)
  6. Validation: All tests pass after each cycle

Examples

Test Generation — Input → Output (Pytest)

Input source function (math_utils.py):

def divide(a: float, b: float) -> float:
    if b == 0:
        raise ValueError("Cannot divide by zero")
    return a / b

Command:

python scripts/test_generator.py --input math_utils.py --framework pytest

Generated test output (test_math_utils.py):

import pytest
from math_utils import divide

class TestDivide:
    def test_divide_positive_numbers(self):
        assert divide(10, 2) == 5.0

    def test_divide_negative_numerator(self):
        assert divide(-10, 2) == -5.0

    def test_divide_float_result(self):
        assert divide(1, 3) == pytest.approx(0.333, rel=1e-3)

    def test_divide_by_zero_raises_value_error(self):
        with pytest.raises(ValueError, match="Cannot divide by zero"):
            divide(10, 0)

    def test_divide_zero_numerator(self):
        assert divide(0, 5) == 0.0

Coverage Analysis — Sample P0/P1/P2 Output

Command:

python scripts/coverage_analyzer.py --report lcov.info --threshold 80

Sample output:

Coverage Report — Overall: 63% (threshold: 80%)

P0 — Critical gaps (uncovered error paths):
  auth/login.py:42-58   handle_expired_token()       0% covered
  payments/process.py:91-110  handle_payment_failure()   0% covered

P1 — High-value gaps (core logic branches):
  users/service.py:77   update_profile() — else branch  0% covered
  orders/cart.py:134    apply_discount() — zero-qty guard  0% covered

P2 — Low-risk gaps (utility / helper functions):
  utils/formatting.py:12  format_currency()            0% covered

Recommended: Generate tests for P0 items first to reach 80% threshold.

Key Tools

ToolPurposeUsage
test_generator.pyGenerate test cases from code/requirementspython scripts/test_generator.py --input source.py --framework pytest
coverage_analyzer.pyParse and analyze coverage reportspython scripts/coverage_analyzer.py --report lcov.info --threshold 80
tdd_workflow.pyGuide red-green-refactor cyclespython scripts/tdd_workflow.py --phase red --test test_auth.py
fixture_generator.pyGenerate test data and mockspython scripts/fixture_generator.py --entity User --count 5

Additional scripts: framework_adapter.py (convert between frameworks), metrics_calculator.py (quality metrics), format_detector.py (detect language/framework), output_formatter.py (CLI/desktop/CI output).


Input Requirements

For Test Generation:

  • Source code (file path or pasted content)
  • Target framework (Jest, Pytest, JUnit, Vitest)
  • Coverage scope (unit, integration, edge cases)

For Coverage Analysis:

  • Coverage report file (LCOV, JSON, or XML format)
  • Optional: Source code for context
  • Optional: Target threshold percentage

For TDD Workflow:

  • Feature requirements or user story
  • Current phase (RED, GREEN, REFACTOR)
  • Test code and implementation status

Limitations

ScopeDetails
Unit test focusIntegration and E2E tests require different patterns
Static analysisCannot execute tests or measure runtime behavior
Language supportBest for TypeScript, JavaScript, Python, Java
Report formatsLCOV, JSON, XML only; other formats need conversion
Generated testsProvide scaffolding; require human review for complex logic

When to use other tools:

  • E2E testing: Playwright, Cypress, Selenium
  • Performance testing: k6, JMeter, Locust
  • Security testing: OWASP ZAP, Burp Suite

Install this Skill

Skills give your AI agent a consistent, structured approach to this task — better output than a one-off prompt.

npx skills add alirezarezvani/claude-skills --skill engineering-team/tdd-guide
Download ZIP

Community skill by @alirezarezvani. Need a walkthrough? See the install guide →

Works with

Prefer no terminal? Download the ZIP and place it manually.

Details

Category
Development
License
MIT
Source file
show path engineering-team/tdd-guide/SKILL.md
TDD testing methodology red-green-refactor