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

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

| Tool | Purpose | Usage | |------|---------|-------| | test_generator.py | Generate test cases from code/requirements | python scripts/test_generator.py --input source.py --framework pytest | | coverage_analyzer.py | Parse and analyze coverage reports | python scripts/coverage_analyzer.py --report lcov.info --threshold 80 | | tdd_workflow.py | Guide red-green-refactor cycles | python scripts/tdd_workflow.py --phase red --test test_auth.py | | fixture_generator.py | Generate test data and mocks | python 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:

For Coverage Analysis:

For TDD Workflow:

Limitations

| Scope | Details | |-------|---------| | Unit test focus | Integration and E2E tests require different patterns | | Static analysis | Cannot execute tests or measure runtime behavior | | Language support | Best for TypeScript, JavaScript, Python, Java | | Report formats | LCOV, JSON, XML only; other formats need conversion | | Generated tests | Provide scaffolding; require human review for complex logic |

When to use other tools:

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.