TDD Guide

The agent guides red-green-refactor TDD workflows, generates framework-specific test stubs from requirements, parses coverage reports to identify prioritized gaps, and calculates test quality metrics including smell detection and assertion density. Supports Jest, Pytest, JUnit, Vitest, and Mocha.

Quick Start

# Generate test cases from requirements (Python API)
from test_generator import TestGenerator, TestFramework
gen = TestGenerator(framework=TestFramework.PYTEST, language="python")
cases = gen.generate_from_requirements(requirements)

# Analyze coverage gaps from LCOV report
from coverage_analyzer import CoverageAnalyzer
analyzer = CoverageAnalyzer()
analyzer.parse_coverage_report(content, "lcov")
gaps = analyzer.identify_gaps(threshold=80.0)

# Guide TDD cycle
from tdd_workflow import TDDWorkflow
wf = TDDWorkflow()
wf.start_cycle("User can reset password via email")

---

Core Workflows

Workflow 1: TDD a New Feature

1. Write a failing test for the feature requirement (RED phase)
2. Call validate_red_phase() -- confirms test exists and fails
3. Write minimal code to make the test pass (GREEN phase)
4. Call validate_green_phase() -- confirms all tests pass
5. Refactor while keeping tests green (REFACTOR phase)
6. Call validate_refactor_phase() -- confirms tests still pass after cleanup
7. Validation checkpoint: Each cycle completes in under 10 minutes; zero test smells introduced

Workflow 2: Analyze Coverage Gaps

1. Generate coverage report: npm test -- --coverage or pytest --cov
2. Detect format with detect_format() and parse with parse_coverage_report()
3. Run identify_gaps(threshold=80.0) to get prioritized file list (P0/P1/P2)
4. Generate test stubs for P0 files (business-critical, lowest coverage)
5. Validation checkpoint: Line coverage >= 80%; branch coverage >= 70%; zero P0 gaps in critical paths

Workflow 3: Generate Tests from Requirements

1. Structure requirements as user stories with acceptance criteria
2. Call generate_from_requirements() with target framework
3. Review generated test cases for completeness (happy path, error, edge cases)
4. Generate test file with generate_test_file()
5. Validation checkpoint: Each acceptance criterion has at least one test; all tests compile

---

Tools

Tool	Purpose
test_generator.py	Generate test cases from requirements/specs
coverage_analyzer.py	Parse LCOV/JSON/XML reports, find gaps
tdd_workflow.py	Guide red-green-refactor cycles
framework_adapter.py	Convert tests between frameworks
fixture_generator.py	Generate test data and mocks with seeds
metrics_calculator.py	Calculate complexity and test quality
format_detector.py	Auto-detect language and framework
output_formatter.py	Format output for CLI/desktop/CI

---

Anti-Patterns

• Tests that pass immediately -- a test with no real assertion or assert True skips the RED phase; every test must fail before implementation
• Testing implementation details -- coupling tests to internal method names makes refactoring break tests; test behavior and outputs, not internals
• Non-deterministic fixtures -- random data without a seed produces different failures across CI runs; always pass seed=<int> to FixtureGenerator
• Skipping the refactor phase -- GREEN code that works but is messy accumulates; refactoring is not optional in TDD
• Coverage theater -- writing tests that hit lines without meaningful assertions; use metrics_calculator.py to detect low assertion density
• Conditional test logic -- if/else inside tests masks failures; each test should have a single clear path

---

Troubleshooting

Problem	Cause	Solution
Generated tests pass immediately (no RED phase)	Test has no real assertion or asserts a trivially true value	Ensure every test contains an assertion against the actual unit under test; remove placeholder assert True stubs before running
Coverage report fails to parse	Report format does not match the expected LCOV, JSON, or XML structure	Run format_detector.py first to verify the detected format; convert non-standard reports (e.g., Clover) to Cobertura XML
Framework adapter produces wrong import style	Source and target framework were swapped, or language/framework mismatch	Verify the framework and language arguments match your project; use detect_framework() on existing test code to auto-detect
Fixture generator produces non-deterministic data	No random seed was supplied, so each run yields different values	Pass seed=<int> to FixtureGenerator() for reproducible fixtures across CI runs
Metrics calculator reports 0 test functions	Test code uses an unsupported naming convention (e.g., spec_ prefix)	Rename tests to follow test_* / it() / @Test conventions, or extend the regex patterns in _count_test_functions()
TDD workflow validates GREEN phase but tests still fail locally	Test result dict passed to validate_green_phase() has status not set to "passed"	Ensure your test runner output is normalized to {"status": "passed"} or {"status": "failed"} before passing it in
Coverage gaps list is empty despite low overall coverage	All individual files meet the threshold even though the aggregate does not	Lower the threshold argument in identify_gaps() or inspect per-file coverage with get_file_coverage()

---

Success Criteria

• Test-first ratio above 80% -- at least 4 out of every 5 features begin with a failing test before any implementation code is written.
• Red-green-refactor cycle under 10 minutes -- each TDD micro-cycle (write failing test, make it pass, refactor) completes within a single focused interval.
• Line coverage at or above 80% -- measured by coverage_analyzer.py against LCOV/JSON/XML reports, with branch coverage at or above 70%.
• Test quality score at or above 75/100 -- as reported by metrics_calculator.py, combining assertion density, isolation, naming quality, and absence of test smells.
• Zero P0 coverage gaps in critical paths -- business-critical modules (auth, payments, data persistence) have no files flagged P0 by identify_gaps().
• Test smell count of zero for high-severity items -- no missing_assertions, sleepy_test, or conditional_test_logic smells detected at high severity.
• Fixture reproducibility across CI -- all generated fixtures use a fixed seed and produce identical output on every pipeline run.

---

Scope & Limitations

This skill covers:

• Unit test generation, scaffolding, and stub creation for Jest, Pytest, JUnit, Vitest, and Mocha
• Static coverage report parsing (LCOV, JSON/Istanbul, XML/Cobertura) with gap identification and prioritized recommendations
• Red-green-refactor workflow guidance with phase validation and cycle tracking
• Test quality assessment including complexity analysis, isolation scoring, naming quality, and test smell detection

This skill does NOT cover:

• Integration, end-to-end, or performance test generation -- see senior-qa for E2E patterns and senior-devops for load testing
• Runtime test execution or live coverage measurement -- scripts perform static analysis only; you must run your test suite externally
• Visual/snapshot testing or browser-based test workflows -- use Playwright, Cypress, or Storybook for UI-level testing
• Security-focused test generation (fuzz testing, penetration testing) -- see senior-security and senior-secops skills

---

Integration Points

Skill	Integration	Data Flow
senior-qa	Generated test stubs feed into QA review workflows; QA coverage standards inform threshold settings	test_generator.py output → QA review → approved test suite
code-reviewer	Metrics calculator output provides quantitative data for code review checklists	metrics_calculator.py quality report → code review scoring
senior-fullstack	Scaffolded projects include test infrastructure; TDD guide generates tests for scaffolded modules	project_scaffolder.py output → test_generator.py input
senior-devops	Coverage reports from CI pipelines are parsed by coverage analyzer; recommendations feed back into pipeline gates	CI coverage artifact → coverage_analyzer.py → pass/fail gate
senior-security	Edge-case fixtures for auth and API scenarios complement security-focused test plans	fixture_generator.py auth/API edge cases → security test plan
tech-stack-evaluator	Framework detection informs stack evaluation; test quality metrics feed into technology assessment	format_detector.py analysis → stack evaluation input

---

Tool Reference

1. test_generator.py

Purpose: Generate test cases from requirements, user stories, and API specs, then produce framework-specific test stubs and complete test files.

Module: TestGenerator class

Usage:

from test_generator import TestGenerator, TestFramework, TestType

gen = TestGenerator(framework=TestFramework.PYTEST, language="python")
cases = gen.generate_from_requirements(requirements, test_type=TestType.UNIT)
stub = gen.generate_test_stub(cases[0])
file_content = gen.generate_test_file("my_module", cases)
suggestions = gen.suggest_missing_scenarios(existing_tests, code_analysis)

Constructor Parameters:

Parameter	Type	Required	Description
framework	TestFramework	Yes	Target framework: JEST, VITEST, PYTEST, JUNIT, MOCHA
language	str	Yes	Programming language: typescript, javascript, python, java

Key Methods:

Method	Parameters	Returns
generate_from_requirements(requirements, test_type)	requirements: dict with user_stories, acceptance_criteria, api_specs; test_type: TestType enum (default UNIT)	List[Dict] of test case specs
generate_test_stub(test_case)	test_case: single test case dict	str -- framework-specific test stub code
generate_test_file(module_name, test_cases)	module_name: str; test_cases: optional list (uses stored cases if omitted)	str -- complete test file with imports
suggest_missing_scenarios(existing_tests, code_analysis)	existing_tests: list of test name strings; code_analysis: dict with error_handlers, conditional_branches, input_validation	List[Dict] of suggested test scenarios

Output Formats: Python dict/list (test case specifications), string (generated code).

Example:

requirements = {
    "user_stories": [{"action": "login", "given": ["valid credentials"], "when": "submit form", "then": "redirect to dashboard"}],
    "api_specs": [{"method": "POST", "path": "/auth/login", "requires_auth": False, "required_params": ["email", "password"]}]
}
gen = TestGenerator(framework=TestFramework.JEST, language="typescript")
cases = gen.generate_from_requirements(requirements)
print(gen.generate_test_file("auth_service", cases))

---

2. coverage_analyzer.py

Purpose: Parse coverage reports in LCOV, JSON (Istanbul/nyc), and XML (Cobertura) formats. Calculate summary metrics, identify files below threshold, and generate prioritized recommendations.

Module: CoverageAnalyzer class

Usage:

from coverage_analyzer import CoverageAnalyzer

analyzer = CoverageAnalyzer()
data = analyzer.parse_coverage_report(report_content, format_type="lcov")
summary = analyzer.calculate_summary()
gaps = analyzer.identify_gaps(threshold=80.0)
recs = analyzer.generate_recommendations()
file_detail = analyzer.get_file_coverage("src/auth.ts")
detected = analyzer.detect_format(raw_content)

Constructor Parameters: None.

Key Methods:

Method	Parameters	Returns
parse_coverage_report(report_content, format_type)	report_content: str; format_type: "lcov", "json", "xml", "cobertura"	Dict of per-file coverage data
calculate_summary()	None	Dict with line_coverage, branch_coverage, function_coverage, totals
identify_gaps(threshold)	threshold: float (default 80.0)	List[Dict] of files below threshold with priority P0/P1/P2
generate_recommendations()	None	List[Dict] of prioritized recommendations
get_file_coverage(file_path)	file_path: str	Dict with per-file line/branch/function coverage
detect_format(content)	content: str	str -- "lcov", "json", or "xml"

Output Formats: Python dict/list. Use output_formatter.py for terminal/markdown/JSON rendering.

Example:

with open("coverage/lcov.info") as f:
    content = f.read()
analyzer = CoverageAnalyzer()
fmt = analyzer.detect_format(content)
analyzer.parse_coverage_report(content, fmt)
summary = analyzer.calculate_summary()
# {'line_coverage': 76.5, 'branch_coverage': 62.3, ...}
gaps = analyzer.identify_gaps(threshold=80.0)
# [{'file': 'src/auth.ts', 'line_coverage': 45.0, 'priority': 'P0', ...}]

---

3. tdd_workflow.py

Purpose: Guide users through red-green-refactor TDD cycles with phase validation, workflow state tracking, and refactoring suggestions.

Module: TDDWorkflow class

Usage:

from tdd_workflow import TDDWorkflow

wf = TDDWorkflow()
guidance = wf.start_cycle("User can reset password via email")
red_result = wf.validate_red_phase(test_code, test_result={"status": "failed"})
green_result = wf.validate_green_phase(impl_code, {"status": "passed"})
refactor_result = wf.validate_refactor_phase(original, refactored, {"status": "passed"})
phase_guide = wf.get_phase_guidance()
summary = wf.generate_workflow_summary()

Constructor Parameters: None.

Key Methods:

Method	Parameters	Returns
start_cycle(requirement)	requirement: str -- user story or feature description	Dict with phase, instruction, checklist, tips
validate_red_phase(test_code, test_result)	test_code: str; test_result: optional dict with status key	Dict with phase_complete, validations, next instruction
validate_green_phase(implementation_code, test_result)	implementation_code: str; test_result: dict with status key	Dict with phase_complete, validations, refactoring_suggestions
validate_refactor_phase(original_code, refactored_code, test_result)	original_code: str; refactored_code: str; test_result: dict with status key	Dict with phase_complete, cycle_complete, next steps
get_phase_guidance(phase)	phase: optional TDDPhase enum (uses current phase if omitted)	Dict with goal, steps, common mistakes, tips
generate_workflow_summary()	None	str -- markdown summary of current state and completed cycles

Output Formats: Python dict (validation results), string (summary).

Example:

wf = TDDWorkflow()
wf.start_cycle("Add email validation to signup form")
result = wf.validate_red_phase("def test_invalid_email():\n    assert validate('bad') == False", {"status": "failed"})
# {'phase_complete': True, 'next_phase': 'GREEN', ...}

---

4. framework_adapter.py

Purpose: Provide multi-framework support with adapters for Jest, Vitest, Pytest, unittest, JUnit, TestNG, Mocha, and Jasmine. Generate framework-specific imports, test suites, test functions, assertions, and setup/teardown hooks.

Module: FrameworkAdapter class

Usage:

from framework_adapter import FrameworkAdapter, Framework, Language

adapter = FrameworkAdapter(framework=Framework.JEST, language=Language.TYPESCRIPT)
imports = adapter.generate_imports()
suite = adapter.generate_test_suite_wrapper("AuthService", test_content)
test_fn = adapter.generate_test_function("should reject invalid email", body, "Validates email format")
assertion = adapter.generate_assertion("result", "true", "true")
hooks = adapter.generate_setup_teardown(setup_code="db = create_test_db()", teardown_code="db.close()")
detected = adapter.detect_framework(existing_code)

Constructor Parameters:

Parameter	Type	Required	Description
framework	Framework	Yes	JEST, VITEST, PYTEST, UNITTEST, JUNIT, TESTNG, MOCHA, JASMINE
language	Language	Yes	TYPESCRIPT, JAVASCRIPT, PYTHON, JAVA

Key Methods:

Method	Parameters	Returns
generate_imports()	None	str -- framework-specific import statements
generate_test_suite_wrapper(suite_name, test_content)	suite_name: str; test_content: str	str -- complete test suite wrapping content
generate_test_function(test_name, test_body, description)	test_name: str; test_body: str; description: str (default "")	str -- complete test function
generate_assertion(actual, expected, assertion_type)	actual: str; expected: str; assertion_type: "equals", "not_equals", "true", "false", "throws" (default "equals")	str -- assertion statement
generate_setup_teardown(setup_code, teardown_code)	setup_code: str (default ""); teardown_code: str (default "")	str -- setup/teardown hooks
detect_framework(code)	code: str	Framework enum or None

Output Formats: String (generated code).

Example:

adapter = FrameworkAdapter(Framework.PYTEST, Language.PYTHON)
print(adapter.generate_imports())
# import pytest
print(adapter.generate_assertion("calculate_total(items)", "150.0", "equals"))
# assert calculate_total(items) == 150.0

---

5. fixture_generator.py

Purpose: Generate realistic test data, boundary values, edge-case scenarios, and mock objects for various domains (auth, payment, form, API, file upload).

Module: FixtureGenerator class

Usage:

from fixture_generator import FixtureGenerator

gen = FixtureGenerator(seed=42)
boundaries = gen.generate_boundary_values("int", {"min": 0, "max": 255})
edge_cases = gen.generate_edge_cases("auth")
mocks = gen.generate_mock_data(schema, count=5)
fixture_content = gen.generate_fixture_file("users", mocks, format="json")

Constructor Parameters:

Parameter	Type	Required	Description
seed	int or None	No	Random seed for reproducible output (default None)

Key Methods:

Method	Parameters	Returns
generate_boundary_values(data_type, constraints)	data_type: "int", "string", "array", "date", "email", "url"; constraints: optional dict (min, max, min_length, max_length, min_size, max_size)	List of boundary values
generate_edge_cases(scenario, context)	scenario: "auth", "payment", "form", "api", "file_upload"; context: optional dict (required for "form" with fields key)	List[Dict] of edge case scenarios
generate_mock_data(schema, count)	schema: dict mapping field names to {"type": ...} defs; count: int (default 1)	List[Dict] of mock objects
generate_fixture_file(fixture_name, data, format)	fixture_name: str; data: any; format: "json", "python", "yaml" (default "json")	str -- fixture file content

Supported Schema Field Types: string, int, float, bool, email, date, array.

Output Formats: Python list/dict (data), string (file content in JSON/Python/YAML).

Example:

gen = FixtureGenerator(seed=123)
schema = {
    "id": {"type": "int", "min": 1, "max": 9999},
    "email": {"type": "email"},
    "active": {"type": "bool"}
}
users = gen.generate_mock_data(schema, count=3)
print(gen.generate_fixture_file("test_users", users, format="json"))

---

6. metrics_calculator.py

Purpose: Calculate comprehensive test and code quality metrics including cyclomatic/cognitive complexity, testability scoring, test quality assessment (assertions, isolation, naming, smells), and execution analysis.

Module: MetricsCalculator class

Usage:

from metrics_calculator import MetricsCalculator

calc = MetricsCalculator()
all_metrics = calc.calculate_all_metrics(source_code, test_code, coverage_data, execution_data)
complexity = calc.calculate_complexity(source_code)
test_quality = calc.calculate_test_quality(test_code)
execution = calc.analyze_execution_metrics(execution_data)
summary = calc.generate_metrics_summary()

Constructor Parameters: None.

Key Methods:

Method	Parameters	Returns
calculate_all_metrics(source_code, test_code, coverage_data, execution_data)	source_code: str; test_code: str; coverage_data: optional dict; execution_data: optional dict	Dict with complexity, test_quality, coverage, execution
calculate_complexity(code)	code: str	Dict with cyclomatic_complexity, cognitive_complexity, testability_score, assessment
calculate_test_quality(test_code)	test_code: str	Dict with total_tests, total_assertions, avg_assertions_per_test, isolation_score, naming_quality, test_smells, quality_score
analyze_execution_metrics(execution_data)	execution_data: dict with tests list (each having duration, status, optional failure_rate)	Dict with total_tests, timing stats, slow_tests, flaky_tests, pass_rate
generate_metrics_summary()	None	str -- human-readable markdown summary

Output Formats: Python dict (metrics data), string (markdown summary).

Example:

calc = MetricsCalculator()
complexity = calc.calculate_complexity(open("src/auth.py").read())
# {'cyclomatic_complexity': 8, 'cognitive_complexity': 12, 'testability_score': 82.0, 'assessment': 'Medium complexity - moderately testable'}
quality = calc.calculate_test_quality(open("tests/test_auth.py").read())
# {'quality_score': 78.5, 'test_smells': [], ...}

---

7. format_detector.py

Purpose: Automatically detect programming language, testing framework, coverage report format, and project structure from code content or file paths.

Module: FormatDetector class

Usage:

from format_detector import FormatDetector

detector = FormatDetector()
language = detector.detect_language(code)
framework = detector.detect_test_framework(test_code)
cov_format = detector.detect_coverage_format(report_content)
input_info = detector.detect_input_format(raw_input)
file_info = detector.extract_file_info("/src/auth.service.ts")
test_name = detector.suggest_test_file_name("auth.service.ts", "jest")
patterns = detector.identify_test_patterns(test_code)
project = detector.analyze_project_structure(file_path_list)
env = detector.detect_environment()

Constructor Parameters: None.

Key Methods:

Method	Parameters	Returns
detect_language(code)	code: str	str -- "typescript", "javascript", "python", "java", "unknown"
detect_test_framework(code)	code: str	str -- "jest", "vitest", "pytest", "unittest", "junit", "mocha", "unknown"
detect_coverage_format(content)	content: str	str -- "lcov", "json", "xml", "unknown"
detect_input_format(input_data)	input_data: str	Dict with format, language, framework, content_type
extract_file_info(file_path)	file_path: str	Dict with file_name, extension, language, is_test, purpose
suggest_test_file_name(source_file, framework)	source_file: str; framework: str	str -- suggested test file name
identify_test_patterns(code)	code: str	List[str] of detected patterns (AAA, Given-When-Then, etc.)
analyze_project_structure(file_paths)	file_paths: list of str	Dict with primary_language, test_ratio, suggested_framework
detect_environment()	None	Dict with environment, output_preference

Output Formats: String (detection result), Python dict (detailed analysis).

Example:

detector = FormatDetector()
print(detector.detect_language("const add = (a: number, b: number): number => a + b;"))
# "typescript"
print(detector.suggest_test_file_name("UserService.java", "junit"))
# "UserserviceTest.java"
print(detector.identify_test_patterns("// Arrange\nsetup()\n// Act\nresult = run()\n// Assert\nassert result"))
# ['AAA (Arrange-Act-Assert)']

---

8. output_formatter.py

Purpose: Context-aware output formatting for different environments (Desktop/markdown, CLI/terminal, API/JSON). Supports progressive disclosure, token-efficient summary reports, and output truncation.

Module: OutputFormatter class

Usage:

from output_formatter import OutputFormatter

fmt = OutputFormatter(environment="cli", verbose=False)
cov_output = fmt.format_coverage_summary(summary, detailed=True)
rec_output = fmt.format_recommendations(recommendations, max_items=5)
test_output = fmt.format_test_results(results, show_details=True)
report = fmt.create_summary_report(coverage, metrics, recommendations)
should_detail = fmt.should_show_detailed(data_size=50)
truncated = fmt.truncate_output(long_text, max_lines=30)

Constructor Parameters:

Parameter	Type	Required	Description
environment	str	No	Target environment: "desktop", "cli", "api" (default "cli")
verbose	bool	No	Include detailed output (default False)

Key Methods:

Method	Parameters	Returns
format_coverage_summary(summary, detailed)	summary: dict; detailed: bool (default False)	str -- formatted coverage (markdown/terminal/JSON based on environment)
format_recommendations(recommendations, max_items)	recommendations: list of dicts; max_items: optional int	str -- formatted recommendations grouped by priority
format_test_results(results, show_details)	results: dict with total_tests, passed, failed, skipped, failed_tests; show_details: bool (default False)	str -- formatted test results
create_summary_report(coverage, metrics, recommendations)	coverage: dict; metrics: dict; recommendations: list	str -- token-efficient summary (<200 tokens)
should_show_detailed(data_size)	data_size: int	bool -- whether to show detailed output
truncate_output(text, max_lines)	text: str; max_lines: int (default 50)	str -- truncated text with remaining-lines indicator

Output Formats: String in markdown (desktop), plain text (CLI), or JSON (API) depending on environment setting.

Example:

fmt = OutputFormatter(environment="desktop", verbose=True)
print(fmt.format_coverage_summary({"line_coverage": 82.5, "branch_coverage": 71.0, "function_coverage": 90.0}))
# ## Test Coverage Summary
# ### Overall Metrics
# - **Line Coverage**: 82.5%
# ...