Agent skill

generate-test

Generate Jest test suite with mocks and common test cases. Use when creating tests for components, repositories, or API routes.

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npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/data/generate-test

SKILL.md

Generate Test

Generate a Jest test suite following Health Tracker 9000 testing patterns.

Usage

When user requests to create tests, ask for:

  1. Test target (component, repository, API route, or utility)
  2. Target name (e.g., "MealLogForm", "WaterLogRepository")
  3. Main functionality to test
  4. Edge cases or error scenarios

Implementation Pattern

Based on src/__tests__/components/forms/MealLogForm.test.tsx pattern.

Component Test Structure

Create file: src/__tests__/{target-type}/{location}/{TargetName}.test.tsx

typescript
import { render, screen, fireEvent, waitFor } from '@testing-library/react';
import { FormName } from '@/components/forms/FormName';
import { useHealthStore } from '@/lib/store/healthStore';

// Mock the store
jest.mock('@/lib/store/healthStore');
jest.mock('sonner', () => ({
  toast: {
    success: jest.fn(),
    error: jest.fn(),
    info: jest.fn(),
  },
}));

const mockAddItem = jest.fn();

describe('FormName', () => {
  beforeEach(() => {
    jest.clearAllMocks();
    (useHealthStore as jest.Mock).mockReturnValue({
      addItem: mockAddItem,
      isLoading: false,
    });
  });

  it('renders the form correctly', () => {
    render(<FormName />);
    expect(screen.getByLabelText('Field 1 Label')).toBeInTheDocument();
    expect(screen.getByLabelText('Field 2 Label')).toBeInTheDocument();
    expect(screen.getByRole('button', { name: /submit/i })).toBeInTheDocument();
  });

  it('validates required fields', async () => {
    render(<FormName />);
    const submitButton = screen.getByRole('button', { name: /submit/i });
    fireEvent.click(submitButton);
    await waitFor(() => {
      expect(screen.getByText('Field 1 is required')).toBeInTheDocument();
    });
  });

  it('submits form with valid data', async () => {
    render(<FormName />);
    const field1Input = screen.getByLabelText('Field 1 Label') as HTMLInputElement;
    const field2Input = screen.getByLabelText('Field 2 Label') as HTMLInputElement;
    const submitButton = screen.getByRole('button', { name: /submit/i });

    fireEvent.change(field1Input, { target: { value: 'test value' } });
    fireEvent.change(field2Input, { target: { value: '100' } });
    fireEvent.click(submitButton);

    await waitFor(() => {
      expect(mockAddItem).toHaveBeenCalledWith(
        expect.objectContaining({
          field1: 'test value',
          field2: '100',
        })
      );
    });
  });

  it('clears form after successful submission', async () => {
    render(<FormName />);
    const field1Input = screen.getByLabelText('Field 1 Label') as HTMLInputElement;
    const submitButton = screen.getByRole('button', { name: /submit/i });

    fireEvent.change(field1Input, { target: { value: 'test' } });
    fireEvent.click(submitButton);

    await waitFor(() => {
      expect(field1Input.value).toBe('');
    });
  });

  it('disables form while loading', () => {
    (useHealthStore as jest.Mock).mockReturnValue({
      addItem: mockAddItem,
      isLoading: true,
    });

    render(<FormName />);
    const submitButton = screen.getByRole('button', { name: /submit/i });
    expect(submitButton).toBeDisabled();
  });
});

Repository Test Structure

Create file: src/__tests__/lib/database/repositories/{EntityName}.test.ts

typescript
import { EntityRepository } from '@/lib/database/repositories/entityRepository';
import { getDatabase } from '@/lib/database/connection';

jest.mock('@/lib/database/connection');

describe('EntityRepository', () => {
  let repo: EntityRepository;
  let mockDb: any;

  beforeEach(() => {
    jest.clearAllMocks();
    mockDb = {
      prepare: jest.fn(),
    };
    (getDatabase as jest.Mock).mockReturnValue(mockDb);
    repo = new EntityRepository();
  });

  it('adds entity correctly', () => {
    const mockStmt = { run: jest.fn() };
    mockDb.prepare.mockReturnValue(mockStmt);

    const result = repo.addEntity({ field1: 'value1', field2: 'value2' });

    expect(result).toHaveProperty('id');
    expect(result).toHaveProperty('createdAt');
    expect(result.field1).toBe('value1');
    expect(mockStmt.run).toHaveBeenCalled();
  });

  it('gets entity by id', () => {
    const mockStmt = { get: jest.fn() };
    mockDb.prepare.mockReturnValue(mockStmt);
    mockStmt.get.mockReturnValue({
      id: '123',
      field_1: 'value1',
      field_2: '{"nested": "data"}',
    });

    const result = repo.getEntityById('123');

    expect(result).toEqual(
      expect.objectContaining({
        id: '123',
        field1: 'value1',
      })
    );
  });

  it('returns null for non-existent entity', () => {
    const mockStmt = { get: jest.fn() };
    mockDb.prepare.mockReturnValue(mockStmt);
    mockStmt.get.mockReturnValue(undefined);

    const result = repo.getEntityById('nonexistent');

    expect(result).toBeNull();
  });

  it('throws error when updating non-existent entity', () => {
    const mockStmt = { get: jest.fn() };
    mockDb.prepare.mockReturnValue(mockStmt);
    mockStmt.get.mockReturnValue(undefined);

    expect(() => {
      repo.updateEntity('nonexistent', {});
    }).toThrow('Entity not found');
  });

  it('deletes entity correctly', () => {
    const mockStmt = { run: jest.fn() };
    mockDb.prepare.mockReturnValue(mockStmt);

    repo.deleteEntity('123');

    expect(mockStmt.run).toHaveBeenCalledWith('123');
  });
});

API Route Test Structure

Create file: src/__tests__/app/api/{resource}/route.test.ts

typescript
import { POST, DELETE } from '@/app/api/resource/route';
import { ResourceRepository } from '@/lib/database/repositories/resourceRepository';

jest.mock('@/lib/database/repositories/resourceRepository');
jest.mock('@/lib/database/repositories/dailySummaryRepository');

describe('Resource API Route', () => {
  beforeEach(() => {
    jest.clearAllMocks();
  });

  it('POST creates new resource', async () => {
    const mockRepo = {
      addResource: jest.fn().mockReturnValue({ id: '123', field: 'value' }),
    };
    (ResourceRepository as jest.Mock).mockImplementation(() => mockRepo);

    const request = new Request('http://localhost:3000/api/resource', {
      method: 'POST',
      body: JSON.stringify({ field: 'value', date: '2024-01-15' }),
    });

    const response = await POST(request);
    const data = await response.json();

    expect(response.status).toBe(200);
    expect(data).toEqual({ id: '123', field: 'value' });
  });

  it('DELETE removes resource', async () => {
    const mockRepo = { deleteResource: jest.fn() };
    (ResourceRepository as jest.Mock).mockImplementation(() => mockRepo);

    const request = new Request('http://localhost:3000/api/resource?id=123', {
      method: 'DELETE',
    });

    const response = await DELETE(request);

    expect(response.status).toBe(200);
    expect(mockRepo.deleteResource).toHaveBeenCalledWith('123');
  });

  it('DELETE returns 400 when id missing', async () => {
    const request = new Request('http://localhost:3000/api/resource', {
      method: 'DELETE',
    });

    const response = await DELETE(request);

    expect(response.status).toBe(400);
  });
});

Key Conventions

  • Test file location mirrors source structure in src/__tests__/
  • File naming: {SourceName}.test.ts(x)
  • Mock external dependencies (stores, API calls, database)
  • beforeEach to clear mocks between tests
  • Use React Testing Library patterns for components
  • Test user interactions, not implementation
  • Test error cases and edge cases
  • Use descriptive test names (should be readable as documentation)
  • Mock data should be realistic

Test Coverage Targets

For components:

  • Renders correctly
  • Handles user input
  • Validates data
  • Shows error states
  • Manages loading states
  • Calls store actions

For repositories:

  • CRUD operations work
  • Row mapping correct
  • Error handling
  • Null checks

For API routes:

  • POST creates records
  • GET retrieves records
  • DELETE removes records
  • Error handling (400, 500)
  • Proper HTTP status codes

Steps

  1. Ask user for test target, name, and functionality
  2. Create file: src/__tests__/{path}/{Name}.test.ts(x)
  3. Mock dependencies (stores, database, APIs)
  4. Write beforeEach to clear mocks
  5. Write test cases for main functionality
  6. Write test cases for error scenarios
  7. Format with Prettier

Implementation Checklist

  • Test file in correct location
  • Dependencies properly mocked
  • beforeEach clears mocks
  • Tests use descriptive names
  • Main functionality tested
  • Error cases tested
  • Edge cases tested
  • Uses appropriate testing library
  • No implementation details tested
  • Proper assertions used

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