react18-enzyme-to-rtl - Claude MCP Skill

# React 18 Enzyme → RTL Migration

Enzyme has no React 18 adapter and no React 18 support path. All Enzyme tests must be rewritten using React Testing Library.

## The Philosophy Shift (Read This First)

Enzyme tests implementation. RTL tests behavior.

```jsx
// Enzyme: tests that the component has the right internal state
expect(wrapper.state('count')).toBe(3);
expect(wrapper.instance().handleClick).toBeDefined();
expect(wrapper.find('Button').prop('disabled')).toBe(true);

// RTL: tests what the user actually sees and can do
expect(screen.getByText('Count: 3')).toBeInTheDocument();
expect(screen.getByRole('button', { name: /submit/i })).toBeDisabled();
```

This is not a 1:1 translation. Enzyme tests that verify internal state or instance methods don't have RTL equivalents - because RTL intentionally doesn't expose internals. **Rewrite the test to assert the visible outcome instead.**

## API Map

For complete before/after code for each Enzyme API, read:
- **`references/enzyme-api-map.md`** - full mapping: shallow, mount, find, simulate, prop, state, instance, configure
- **`references/async-patterns.md`** - waitFor, findBy, act(), Apollo MockedProvider, loading states, error states

## Core Rewrite Template

```jsx
// Every Enzyme test rewrites to this shape:
import { render, screen, fireEvent, waitFor } from '@testing-library/react';
import userEvent from '@testing-library/user-event';
import MyComponent from './MyComponent';

describe('MyComponent', () => {
  it('does the thing', async () => {
    // 1. Render (replaces shallow/mount)
    render(<MyComponent prop="value" />);

    // 2. Query (replaces wrapper.find())
    const button = screen.getByRole('button', { name: /submit/i });

    // 3. Interact (replaces simulate())
    await userEvent.setup().click(button);

    // 4. Assert on visible output (replaces wrapper.state() / wrapper.prop())
    expect(screen.getByText('Submitted!')).toBeInTheDocument();
  });
});
```

## RTL Query Priority (use in this order)

1. `getByRole` - matches accessible roles (button, textbox, heading, checkbox, etc.)
2. `getByLabelText` - form fields linked to labels
3. `getByPlaceholderText` - input placeholders
4. `getByText` - visible text content
5. `getByDisplayValue` - current value of input/select/textarea
6. `getByAltText` - image alt text
7. `getByTitle` - title attribute
8. `getByTestId` - `data-testid` attribute (last resort)

Prefer `getByRole` over `getByTestId`. It tests accessibility too.

## Wrapping with Providers

```jsx
// Enzyme with context:
const wrapper = mount(
  <ApolloProvider client={client}>
    <ThemeProvider theme={theme}>
      <MyComponent />
    </ThemeProvider>
  </ApolloProvider>
);

// RTL equivalent (use your project's customRender or wrap inline):
import { render } from '@testing-library/react';
render(
  <MockedProvider mocks={mocks} addTypename={false}>
    <ThemeProvider theme={theme}>
      <MyComponent />
    </ThemeProvider>
  </MockedProvider>
);
// Or use the project's customRender helper if it wraps providers
```