TDD Guide

# tdd-guide

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
Provide source code (TypeScript, JavaScript, Python, Java)
Specify target framework (Jest, Pytest, JUnit, Vitest)
Run test_generator.py with requirements
Review generated test stubs
Validation: Tests compile and cover happy path, error cases, edge cases
Analyze Coverage Gaps
Generate coverage report from test runner (npm test -- --coverage)
Run coverage_analyzer.py on LCOV/JSON/XML report
Review prioritized gaps (P0/P1/P2)
Generate missing tests for uncovered paths
Validation: Coverage meets target threshold (typically 80%+)
TDD New Feature
Write failing test first (RED)
Run tdd_workflow.py --phase red to validate
Implement minimal code to pass (GREEN)
Run tdd_workflow.py --phase green to validate
Refactor while keeping tests green (REFACTOR)
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
ToolPurposeUsagetest_generator.pyGenerate test cases from code/requirementspython scripts/test_generator.py --input source.py --framework pytestcoverage_analyzer.pyParse and analyze coverage reportspython scripts/coverage_analyzer.py --report lcov.info --threshold 80tdd_workflow.pyGuide red-green-refactor cyclespython scripts/tdd_workflow.py --phase red --test test_auth.pyfixture_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
ScopeDetailsUnit test focusIntegration and E2E tests require different patternsStatic analysisCannot execute tests or measure runtime behaviorLanguage supportBest for TypeScript, JavaScript, Python, JavaReport formatsLCOV, JSON, XML only; other formats need conversionGenerated 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