PDD-CLI Bug: Generates Features Without Corresponding Test Coverage

## PDD-CLI Bug: Generates Features Without Corresponding Test Coverage

PDD-CLI implements new features but doesn't generate tests for them. Features ship without validation that they work correctly.

**Why this matters:** Bugs aren't caught until production, technical debt accumulates, refactoring becomes risky.

## Concrete Example

For a YAML template rendering feature:

```python
# PDD generated feature (NO TESTS):
# template_renderer.py
import yaml
from jinja2 import Template

def render_yaml_template(template_path: str, data: dict) -> str:
    """Render YAML template with Jinja2."""
    with open(template_path) as f:
        template_content = f.read()
    
    template = Template(template_content)
    rendered = template.render(**data)
    
    # Parse to validate YAML
    yaml.safe_load(rendered)
    
    return rendered
```

But no tests exist:

```python
# tests/test_template_renderer.py
# FILE DOESN'T EXIST!
```

**What went wrong:** PDD implemented template rendering but didn't generate tests to verify it handles edge cases (missing files, invalid YAML, special characters, etc.).

**Impact:** Feature ships untested. First user discovers bugs in production (file not found, YAML parsing errors, etc.).

## Why PDD Makes This Mistake

PDD-CLI currently:
- Focuses on feature implementation
- Treats testing as separate step
- Doesn't follow TDD (Test-Driven Development)

But it should:
1. Generate tests alongside feature code
2. Cover happy path and edge cases
3. Validate error handling

## How to Prevent This in PDD-CLI

**What PDD should do differently:**

1. **Generate tests with features (TDD approach):**
   ```python
   # tests/test_template_renderer.py
   import pytest
   from template_renderer import render_yaml_template
   
   def test_render_yaml_template_basic():
       result = render_yaml_template('templates/test.yaml', {'name': 'Alice'})
       assert 'Alice' in result
       assert yaml.safe_load(result)  # Valid YAML
   
   def test_render_yaml_template_missing_file():
       with pytest.raises(FileNotFoundError):
           render_yaml_template('nonexistent.yaml', {})
   
   def test_render_yaml_template_invalid_yaml():
       with pytest.raises(yaml.YAMLError):
           render_yaml_template('templates/invalid.yaml', {})
   ```

2. **Calculate test coverage:** Ensure generated tests cover main paths.

3. **Generate test data/fixtures:** Create sample templates for testing.

**Example improvement:**
```
Current: "Add YAML template rendering"
       → Generate template_renderer.py
       → No tests
       → Bugs found in production

Improved: "Add YAML template rendering"
        → Generate template_renderer.py
        → Generate test_template_renderer.py
        → Generate test fixtures (sample templates)
        → Run tests to validate
        → Confident feature works correctly
```

## Severity

**P2 - Medium Priority**

- **Frequency:** High - affects all new features
- **Impact:** Medium - technical debt, bugs in production
- **Detectability:** Low - absence of tests is passive
- **Prevention cost:** Medium - requires test generation logic

## Category

`incomplete-implementation`

## Related Issues

- #432 - Data models without extraction logic (similar incomplete pipeline)
- #435 - Incomplete metric calculations (similar partial implementation)
- All other issues - tests would have caught these bugs earlier!

---

**For Contributors:** Discovered when YAML template rendering was added without tests, manual tests added later in commit `34a651d5`. Tests should be generated alongside features.


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PDD-CLI Bug: Generates Features Without Corresponding Test Coverage #589