Testing Agent

3. Test Execution & Analysis

• Test Runners: pytest, tox, coverage.py
• CI/CD Integration: GitHub Actions, Jenkins, GitLab CI
• Coverage Analysis: Line coverage, branch coverage, mutation testing
• Failure Analysis: Root cause identification, flaky test detection
• Performance Profiling: Identifying slow tests, optimization

4. Quality Assurance

• Static Analysis: mypy, pylint, flake8, ruff
• Code Quality: Code smells, complexity analysis
• Test Quality: Test coverage metrics, mutation score
• Regression Prevention: Test for bugs, prevent recurrence

When This Skill Activates

Use this skill when user says:

• "Write tests for..."
• "Run the tests"
• "Check test coverage"
• "Design test cases"
• "Fix failing tests"
• "Implement TDD"
• "Test this feature"
• "Ensure quality"

Testing Process

Phase 1: Test Strategy Design

1.1 Analyze Requirements

• Functional Requirements: What should the code do?
• Edge Cases: What are the boundaries and special cases?
• Error Conditions: What can go wrong?
• Performance Requirements: What are the targets?
• Security Requirements: What needs protection?

1.2 Design Test Plan

# Test Plan: [Feature Name]

## Test Scope
- **In Scope**: [What we're testing]
- **Out of Scope**: [What we're not testing]

## Test Levels
- **Unit Tests**: [Component-level tests]
- **Integration Tests**: [Component interaction tests]
- **E2E Tests**: [Full system tests]

## Test Cases

### Unit Tests
| Test ID | Description | Input | Expected Output | Priority |
|---------|-------------|-------|-----------------|----------|
| UT-001 | Valid input | {...} | Success | High |
| UT-002 | Empty input | [] | EmptyError | High |
| UT-003 | Invalid type | "wrong" | TypeError | High |

### Integration Tests
| Test ID | Description | Setup | Expected | Priority |
|---------|-------------|-------|----------|----------|
| IT-001 | Database integration | Mock DB | Data stored | High |

### Edge Cases
| Test ID | Description | Condition | Expected |
|---------|-------------|-----------|----------|
| EC-001 | Boundary value | Max int | No overflow |
| EC-002 | Null handling | None input | Graceful error |

## Coverage Goals
- **Line Coverage**: >90%
- **Branch Coverage**: >85%
- **Critical Path Coverage**: 100%

## Test Environment
- **Dependencies**: [Mock services, test databases]
- **Fixtures**: [Shared test data]
- **Setup/Teardown**: [Before/after logic]

Phase 2: Test Implementation

2.1 Unit Test Template

"""
Unit tests for [module_name].

Test coverage for [component] including:
- Happy path scenarios
- Edge cases
- Error conditions
- Boundary values
"""

import pytest
from unittest.mock import Mock, patch, AsyncMock
from typing import List

from module_name import ClassName, function_name


class TestClassName:
    """Test suite for ClassName."""

    @pytest.fixture
    def instance(self):
        """Create a test instance."""
        return ClassName(dependency=Mock())

    @pytest.fixture
    def sample_data(self):
        """Provide sample test data."""
        return {
            "key": "value",
            "count": 42
        }

    # Happy Path Tests
    def test_basic_functionality(self, instance, sample_data):
        """Test basic operation with valid input.

        Given: A valid instance and sample data
        When: Method is called with valid parameters
        Then: Expected result is returned
        """
        # Arrange
        expected = "expected_result"

        # Act
        result = instance.method(sample_data)

        # Assert
        assert result == expected

    @pytest.mark.asyncio
    async def test_async_operation(self, instance):
        """Test asynchronous operation.

        Given: An async method
        When: Called with valid input
        Then: Awaitable returns expected result
        """
        # Arrange
        expected = {"status": "success"}

        # Act
        result = await instance.async_method()

        # Assert
        assert result == expected

    # Edge Case Tests
    def test_empty_input(self, instance):
        """Test handling of empty input.

        Given: Empty input data
        When: Method is called
        Then: Appropriate default or error is returned
        """
        # Arrange
        empty_input = []

        # Act & Assert
        with pytest.raises(ValueError, match="Input cannot be empty"):
            instance.method(empty_input)

    def test_none_input(self, instance):
        """Test handling of None input.

        Given: None as input
        When: Method is called
        Then: TypeError is raised
        """
        # Act & Assert
        with pytest.raises(TypeError):
            instance.method(None)

    @pytest.mark.parametrize("invalid_input,expected_error", [
        ("string", TypeError),
        (-1, ValueError),
        (float('inf'), ValueError),
    ])
    def test_invalid_inputs(self, instance, invalid_input, expected_error):
        """Test various invalid inputs raise appropriate errors."""
        with pytest.raises(expected_error):
            instance.method(invalid_input)

    # Boundary Tests
    @pytest.mark.parametrize("boundary_value", [
        0,  # Minimum
        100,  # Maximum
        50,  # Middle
    ])
    def test_boundary_values(self, instance, boundary_value):
        """Test behavior at boundary values."""
        result = instance.method(boundary_value)
        assert 0 <= result <= 100

    # Error Condition Tests
    def test_dependency_failure(self, instance):
        """Test graceful handling of dependency failure.

        Given: A dependency that fails
        When: Method is called
        Then: Error is handled gracefully
        """
        # Arrange
        instance.dependency.call = Mock(side_effect=Exception("Dependency failed"))

        # Act & Assert
        with pytest.raises(DependencyError, match="Dependency failed"):
            instance.method("input")

    @patch('module_name.external_service')
    def test_external_service_timeout(self, mock_service, instance):
        """Test timeout handling for external service."""
        # Arrange
        mock_service.call = AsyncMock(side_effect=TimeoutError())

        # Act
        result = instance.method_with_timeout()

        # Assert
        assert result is None  # Graceful degradation

    # State Tests
    def test_state_change(self, instance):
        """Test that method correctly changes internal state."""
        # Arrange
        initial_state = instance.state

        # Act
        instance.change_state("new_state")

        # Assert
        assert instance.state != initial_state
        assert instance.state == "new_state"

    # Integration Points
    @pytest.mark.integration
    async def test_database_integration(self, instance):
        """Test integration with database.

        Requires: Test database setup
        """
        # Arrange
        test_data = {"id": "test-123", "value": "test"}

        # Act
        await instance.save_to_db(test_data)
        result = await instance.load_from_db("test-123")

        # Assert
        assert result["value"] == "test"

    # Performance Tests
    @pytest.mark.performance
    def test_performance_target(self, instance, benchmark):
        """Test that operation meets performance target."""
        # Benchmark with pytest-benchmark
        result = benchmark(instance.expensive_operation)
        assert result is not None

    # Property-Based Tests
    @pytest.mark.hypothesis
    from hypothesis import given, strategies as st

    @given(st.integers(min_value=0, max_value=1000))
    def test_property_always_positive(self, instance, value):
        """Test that result is always positive for valid inputs."""
        result = instance.process(value)
        assert result >= 0

2.2 Integration Test Template

"""
Integration tests for [feature_name].

Tests component interactions and external integrations.
"""

import pytest
import asyncio
from typing import AsyncGenerator

from module import Component, Database, ExternalAPI


class TestFeatureIntegration:
    """Integration tests for feature components."""

    @pytest.fixture(scope="function")
    async def database(self) -> AsyncGenerator[Database, None]:
        """Setup and teardown test database."""
        # Setup
        db = Database(url="postgresql://test")
        await db.connect()
        await db.create_tables()

        yield db

        # Teardown
        await db.drop_tables()
        await db.disconnect()

    @pytest.fixture
    async def external_api(self):
        """Mock external API for testing."""
        mock = MockExternalAPI()
        await mock.start()
        yield mock
        await mock.stop()

    @pytest.mark.integration
    async def test_end_to_end_workflow(self, database, external_api):
        """Test complete workflow from API to database.

        Given: A configured system with database and external API
        When: User request is processed
        Then: Data flows correctly through all components
        """
        # Arrange
        component = Component(database=database, api=external_api)
        user_input = {"action": "create", "data": {"name": "test"}}

        # Act
        result = await component.process_request(user_input)

        # Assert - verify API was called
        assert external_api.call_count == 1

        # Assert - verify database was updated
        db_record = await database.get("test")
        assert db_record is not None
        assert db_record["name"] == "test"

        # Assert - verify response
        assert result["status"] == "success"

    @pytest.mark.integration
    async def test_transaction_rollback(self, database):
        """Test that transactions rollback on error.

        Given: A database transaction
        When: An error occurs during transaction
        Then: All changes are rolled back
        """
        # Arrange
        initial_count = await database.count_records()

        # Act - transaction that fails
        try:
            async with database.transaction():
                await database.insert({"id": "1", "value": "test"})
                raise ValueError("Simulated error")
        except ValueError:
            pass

        # Assert - no records were inserted
        final_count = await database.count_records()
        assert final_count == initial_count

    @pytest.mark.integration
    async def test_concurrent_access(self, database):
        """Test system under concurrent load.

        Given: Multiple concurrent requests
        When: Processed simultaneously
        Then: All requests complete successfully without conflicts
        """
        # Arrange
        async def concurrent_task(task_id: int):
            result = await database.insert({
                "id": f"task-{task_id}",
                "value": f"value-{task_id}"
            })
            return result

        # Act - run 100 concurrent tasks
        tasks = [concurrent_task(i) for i in range(100)]
        results = await asyncio.gather(*tasks, return_exceptions=True)

        # Assert - all succeeded
        successes = [r for r in results if not isinstance(r, Exception)]
        assert len(successes) == 100

        # Assert - all records in database
        count = await database.count_records()
        assert count == 100

Phase 3: Test Execution

3.1 Run Tests

# Run all tests
pytest

# Run with coverage
pytest --cov=module --cov-report=html --cov-report=term

# Run specific test file
pytest tests/test_feature.py

# Run specific test
pytest tests/test_feature.py::TestClass::test_method

# Run tests by marker
pytest -m "not integration"  # Skip integration tests
pytest -m "unit"              # Only unit tests

# Run with verbose output
pytest -v

# Run failed tests only
pytest --lf

# Run with multiple workers (parallel)
pytest -n auto

# Run with benchmark
pytest --benchmark-only

3.2 Coverage Analysis

# Generate coverage report
coverage run -m pytest
coverage report
coverage html

# Check coverage threshold
coverage report --fail-under=90

# Show missing lines
coverage report -m

# Combine coverage from multiple runs
coverage combine
coverage report

Phase 4: Test Analysis & Reporting

4.1 Test Report Template

# Test Execution Report: [Feature Name]

**Date**: [Current Date]
**Test Suite**: [Suite Name]
**Status**: ✅ Passed | ⚠️ Partial | ❌ Failed

## Summary

- **Total Tests**: 150
- **Passed**: 145 (96.7%)
- **Failed**: 3 (2.0%)
- **Skipped**: 2 (1.3%)
- **Duration**: 12.5s

## Coverage Metrics

- **Line Coverage**: 92% (Target: >90%) ✅
- **Branch Coverage**: 87% (Target: >85%) ✅
- **Function Coverage**: 95%
- **Critical Path Coverage**: 100% ✅

## Test Results by Category

| Category | Total | Passed | Failed | Coverage |
|----------|-------|--------|--------|----------|
| Unit Tests | 100 | 98 | 2 | 94% |
| Integration Tests | 30 | 29 | 1 | 88% |
| E2E Tests | 20 | 18 | 0 | 85% |

## Failed Tests

### 🔴 test_async_timeout (FAILED)
- **File**: `tests/test_feature.py::TestClass::test_async_timeout`
- **Error**: `AssertionError: Expected timeout, got success`
- **Cause**: Timeout threshold too high (30s instead of 5s)
- **Fix**: Update timeout to 5s in test
- **Priority**: High

### 🔴 test_edge_case_large_input (FAILED)
- **File**: `tests/test_edge.py::test_edge_case_large_input`
- **Error**: `MemoryError: Out of memory`
- **Cause**: Test uses 10GB dataset, exceeds CI memory
- **Fix**: Reduce test dataset or mark as manual test
- **Priority**: Medium

### 🔴 test_database_connection (FAILED)
- **File**: `tests/integration/test_db.py::test_database_connection`
- **Error**: `ConnectionError: Database not available`
- **Cause**: Test database not running in CI
- **Fix**: Add database service to CI config
- **Priority**: High

## Coverage Gaps

### Missing Coverage Areas

#### `module/feature.py:line 145-160`
```python
# Not covered by tests
def handle_special_case(data):
    if data.get("special_flag"):
        # This branch never tested
        return process_special(data)
    return process_normal(data)

Recommendation: Add test case for special_flag=True scenario

utils/helpers.py:line 78-92

• Function: parse_complex_input
• Coverage: 0%
• Reason: New function, tests not written yet
• Recommendation: Add comprehensive unit tests

Flaky Tests

⚠️ test_concurrent_requests (Flaky)

• Failure Rate: 5% (3 failures in 60 runs)
• Cause: Race condition in test setup
• Recommendation: Add synchronization or increase timeout

Performance Issues

Slow Tests (>1s)

Security Test Results

Vulnerability Scan

• ✅ No SQL injection vectors found
• ✅ XSS protection verified
• ✅ CSRF tokens validated
• ⚠️ Rate limiting not tested (add test)

Dependency Audit

# Safety check results
safety check
# All dependencies secure ✅

Recommendations

Immediate Actions

1. Fix failed tests (2-3 hours)
2. Add missing test coverage for critical gaps (4 hours)
3. Fix flaky test (1 hour)

Short-term Improvements

1. Add performance tests for key operations
2. Increase integration test coverage to 90%
3. Add contract tests for external APIs

Long-term Enhancements

1. Implement mutation testing
2. Add property-based testing
3. Set up continuous test monitoring

Test Quality Metrics

• Test Code Ratio: 1.2 (1.2 lines of test per line of code)
• Average Test Complexity: Low (good)
• Test Duplication: 3% (acceptable)
• Assertion Density: 2.1 assertions/test (good)

CI/CD Integration Status

• ✅ Tests run on every PR
• ✅ Coverage reports generated
• ✅ Failed tests block merge
• ⚠️ Performance regression detection needed

Approval Status

Test Suite Status: ⚠️ Needs Fixes

Blockers:

• Fix 3 failed tests
• Add coverage for critical gaps
• Fix flaky test

Ready for Production: After blockers addressed

Next Review: After fixes applied

### Phase 5: Test Maintenance

#### 5.1 Fixing Flaky Tests
```python
# ❌ Flaky test (timing-dependent)
def test_async_operation():
    result = start_async_task()
    time.sleep(0.1)  # Race condition!
    assert result.is_complete

# ✅ Fixed test (properly waits)
async def test_async_operation():
    result = await start_async_task()
    await asyncio.wait_for(result.wait_complete(), timeout=5.0)
    assert result.is_complete

5.2 Refactoring Tests

# ❌ Duplicated test setup
def test_feature_a():
    instance = ClassName()
    instance.setup()
    instance.configure({"key": "value"})
    # Test A

def test_feature_b():
    instance = ClassName()
    instance.setup()
    instance.configure({"key": "value"})
    # Test B

# ✅ Shared fixture
@pytest.fixture
def configured_instance():
    instance = ClassName()
    instance.setup()
    instance.configure({"key": "value"})
    return instance

def test_feature_a(configured_instance):
    # Test A

def test_feature_b(configured_instance):
    # Test B

Testing Best Practices

1. Write Tests First (TDD)

Red → Green → Refactor
1. Write failing test
2. Write minimal code to pass
3. Refactor for quality
4. Repeat

2. Test One Thing Per Test

# ❌ Testing multiple things
def test_everything():
    assert function(1) == 2
    assert function(2) == 4
    assert function("x") raises Error
    assert function([]) == []

# ✅ Separate tests
def test_doubles_integer():
    assert function(1) == 2

def test_handles_string_error():
    with pytest.raises(TypeError):
        function("x")

3. Use Descriptive Names

# ❌ Vague name
def test_function():
    ...

# ✅ Descriptive name
def test_calculate_total_returns_sum_of_prices_when_given_valid_cart():
    ...

4. Follow AAA Pattern

def test_feature():
    # Arrange - Set up test data
    input_data = create_test_data()
    expected = "expected_result"

    # Act - Execute the code
    result = function_under_test(input_data)

    # Assert - Verify results
    assert result == expected

5. Use Fixtures for Shared Setup

@pytest.fixture
def database():
    """Provide a test database."""
    db = TestDatabase()
    db.setup()
    yield db
    db.teardown()

6. Mock External Dependencies

@patch('module.external_api')
def test_with_mocked_api(mock_api):
    """Test with external API mocked."""
    mock_api.get.return_value = {"data": "test"}
    result = function_that_calls_api()
    assert result is not None

7. Test Edge Cases

@pytest.mark.parametrize("edge_case", [
    [],           # Empty
    None,         # Null
    [1],          # Single item
    [1] * 1000,   # Large list
    ["special"],  # Special characters
])
def test_edge_cases(edge_case):
    result = handle_input(edge_case)
    assert result is not None

Integration with Other Skills

With principal-engineer:

• Collaborate on test design
• Ensure testable code architecture
• Fix bugs found by tests
• Maintain test quality

With code-reviewer-advanced:

• Report test coverage gaps
• Identify untested code paths
• Validate test quality
• Ensure tests run in CI

With system-architect:

• Design integration test strategy
• Plan E2E test scenarios
• Validate system testability
• Provide test infrastructure requirements

Testing Anti-Patterns

❌ Testing Implementation Details: Test behavior, not internal structure ❌ Fragile Tests: Tests break on every refactoring ❌ Slow Tests: Tests take too long to run ❌ No Assertions: Tests that don't verify anything ❌ Flaky Tests: Tests that randomly fail ❌ Test Everything: 100% coverage of trivial code ❌ No Edge Cases: Only testing happy path ❌ Mocking Everything: Over-mocking loses test value

Test Quality Checklist

Before marking testing complete:

Test Design

• Test plan created
• Test cases identified
• Edge cases considered
• Error conditions planned

Test Implementation

• Unit tests written (70% of tests)
• Integration tests written (20% of tests)
• E2E tests written (10% of tests)
• Tests follow AAA pattern
• Tests have descriptive names
• Fixtures used for shared setup

Test Coverage

• Line coverage >90%
• Branch coverage >85%
• Critical paths 100% covered
• Edge cases tested
• Error conditions tested

Test Quality

• Tests are fast (<1s each)
• Tests are independent
• Tests are repeatable
• No flaky tests
• Tests are maintainable

Test Execution

• All tests pass
• Coverage report generated
• CI/CD integrated
• Failed tests investigated

Remember: Good tests are the foundation of confident refactoring and reliable software. Invest in test quality - it pays dividends throughout the project lifecycle.