tdd

Test-Driven Development for RoboView

Philosophy

Core principle: Tests should verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't.

Good tests are integration-style: they exercise real code paths through public APIs. They describe what the system does, not how it does it.

Bad tests are coupled to implementation. They mock internal collaborators, test private methods, or verify through external means. The warning sign: your test breaks when you refactor, but behavior hasn't changed.

Anti-Pattern: Horizontal Slices

DO NOT write all tests first, then all implementation.

WRONG (horizontal):
  RED:   test1, test2, test3, test4, test5
  GREEN: impl1, impl2, impl3, impl4, impl5

RIGHT (vertical):
  RED→GREEN: test1→impl1
  RED→GREEN: test2→impl2
  RED→GREEN: test3→impl3

Workflow

1. Planning

Before writing any code:

• Confirm with user what interface changes are needed
• Confirm with user which behaviors to test (prioritize)
• Identify opportunities for deep modules (small interface, deep implementation)
• List the behaviors to test (not implementation steps)
• Get user approval on the plan

2. Tracer Bullet

Write ONE test that confirms ONE thing about the system:

RED:   Write test for first behavior → test fails
GREEN: Write minimal code to pass → test passes

3. Incremental Loop

For each remaining behavior:

RED:   Write next test → fails
GREEN: Minimal code to pass → passes

Rules:

• One test at a time
• Only enough code to pass current test
• Don't anticipate future tests
• Keep tests focused on observable behavior

4. Refactor

After all tests pass:

• Extract duplication
• Deepen modules (move complexity behind simple interfaces)
• Apply SOLID principles where natural
• Run tests after each refactor step

Never refactor while RED. Get to GREEN first.

RoboView Backend TDD

Test Structure

# packages/roboview/tests/utest/services_tests/test_new_service.py

import pytest
from uuid import uuid4
from roboview.registries import KeywordRegistry, FileRegistry
from roboview.services import NewService
from roboview.schemas.domain import KeywordProperties

# Test data factories
def _make_keyword(**kwargs) -> KeywordProperties:
    defaults = {
        "keyword_id": uuid4(),
        "file_name": "test.robot",
        "keyword_name_without_prefix": "Test Keyword",
        "keyword_name_with_prefix": "test.Test Keyword",
        "is_user_defined": True,
        "code": "    Log    Hello",
        "source": "/path/to/test.robot",
    }
    defaults.update(kwargs)
    return KeywordProperties(**defaults)

def _make_registries(keywords: list[KeywordProperties]) -> tuple[KeywordRegistry, FileRegistry]:
    kw_registry = KeywordRegistry()
    file_registry = FileRegistry()
    for kw in keywords:
        kw_registry.register(kw)
    return kw_registry, file_registry


class TestNewServiceGetSomething:
    """Tests for NewService.get_something method."""
    
    def test_returns_empty_list_when_no_keywords(self):
        """When registry is empty, should return empty list."""
        kw_registry, file_registry = _make_registries([])
        service = NewService(kw_registry, file_registry)
        
        result = service.get_something()
        
        assert result == []
    
    def test_returns_matching_keywords_when_filter_applies(self):
        """When filter matches, should return matching keywords."""
        keyword = _make_keyword(keyword_name_without_prefix="Matching")
        kw_registry, file_registry = _make_registries([keyword])
        service = NewService(kw_registry, file_registry)
        
        result = service.get_something(filter="Match")
        
        assert len(result) == 1
        assert result[0].keyword_name_without_prefix == "Matching"

Running Tests

# All tests
pytest packages/roboview/tests/utest/ -v

# Specific service tests
pytest packages/roboview/tests/utest/services_tests/test_new_service.py -v

# Specific test method
pytest packages/roboview/tests/utest/services_tests/test_new_service.py -k "test_returns_empty" -v

# With coverage
pytest packages/roboview/tests/utest/ --cov=roboview --cov-report=term-missing

API Endpoint Testing

# packages/roboview/tests/utest/api_tests/test_new_endpoint.py

import pytest
from fastapi.testclient import TestClient
from roboview.main import app

@pytest.fixture
def client():
    return TestClient(app)

def test_endpoint_returns_200_with_valid_data(client, initialized_app):
    """Endpoint should return 200 with properly formatted data."""
    response = client.get("/new-endpoint")
    
    assert response.status_code == 200
    data = response.json()
    assert "expected_key" in data

RoboView Webview TDD

Component Testing Pattern

// vscode-integration/webview-ui/src/__tests__/MetricCard.test.tsx

import { render, screen } from '@testing-library/react';
import { MetricCard } from '../components/MetricCard';

describe('MetricCard', () => {
    it('renders title and value', () => {
        render(<MetricCard title="Keywords" value={42} />);
        
        expect(screen.getByText('Keywords')).toBeInTheDocument();
        expect(screen.getByText('42')).toBeInTheDocument();
    });
    
    it('shows loading skeleton when loading', () => {
        render(<MetricCard title="Keywords" value={null} loading />);
        
        expect(screen.getByTestId('skeleton')).toBeInTheDocument();
    });
});

Hook Testing

import { renderHook, act } from '@testing-library/react';
import { useKeywordData } from '../hooks/useKeywordData';

describe('useKeywordData', () => {
    it('fetches data on mount', async () => {
        const { result } = renderHook(() => useKeywordData());
        
        expect(result.current.loading).toBe(true);
        
        await act(async () => {
            // Simulate message response
        });
        
        expect(result.current.loading).toBe(false);
        expect(result.current.data).toBeDefined();
    });
});

Checklist Per Cycle

[ ] Test describes behavior, not implementation
[ ] Test uses public interface only
[ ] Test would survive internal refactor
[ ] Code is minimal for this test
[ ] No speculative features added