Testing Patterns (@data-client/test)

Hook Testing with renderDataHook()

import { renderDataHook } from '@data-client/test';

it('useSuspense() should render the response', async () => {
  const { result, waitFor } = renderDataHook(
    () => useSuspense(ArticleResource.get, { id: 5 }),
    {
      initialFixtures: [
        {
          endpoint: ArticleResource.get,
          args: [{ id: 5 }],
          response: { id: 5, title: 'hi ho', content: 'whatever' },
        },
      ],
    },
  );
  expect(result.current.title).toBe('hi ho');
});

Options:

• initialFixtures - Set up initial state of the store
• resolverFixtures - Add interceptors for subsequent requests
• getInitialInterceptorData - Simulate changing server state

Return values:

• Inherits all renderHook() return values from @testing-library/react
• controller - Controller instance for manual actions
• allSettled() - Wait for all async operations to complete

Cleanup is automatic -- an afterEach hook is registered at module load time that drains all active cleanups. No manual renderDataHook.cleanup() calls are needed.

Fixtures and Interceptors

Success Fixture:

interface SuccessFixture {
  endpoint;
  args;
  response;
  error?;
  delay?;
}

Response Interceptor:

interface ResponseInterceptor {
  endpoint;
  response(...args);
  delay?;
  delayCollapse?;
}

Testing Mutations

Create operations:

it('should create a new todo', async () => {
  const { result } = renderDataHook(
    () => useController(),
    {
      initialFixtures: [
        {
          endpoint: TodoResource.getList,
          args: [],
          response: [],
        },
      ],
      resolverFixtures: [
        {
          endpoint: TodoResource.getList.push,
          response: (newTodo) => ({ ...newTodo, id: 1 }),
        },
      ],
    },
  );

  const newTodo = { title: 'Test Todo', completed: false };
  const createdTodo = await result.current.fetch(TodoResource.getList.push, newTodo);
  
  expect(createdTodo.id).toBe(1);
});

Testing Error States

it('should handle fetch errors', async () => {
  const { result, waitFor } = renderDataHook(
    () => useSuspense(TodoResource.get, { id: 1 }),
    {
      initialFixtures: [
        {
          endpoint: TodoResource.get,
          args: [{ id: 1 }],
          response: null,
          error: new Error('Not found'),
        },
      ],
    },
  );

  await waitFor(() => {
    expect(result.current).toBeUndefined();
  });
});

Testing Components

Use MockResolver to provide fixture data when rendering components with DataProvider:

import { render } from '@testing-library/react';
import { DataProvider } from '@data-client/react';
import { MockResolver } from '@data-client/test';

it('should render todo list', async () => {
  const fixtures = [
    {
      endpoint: TodoResource.getList,
      args: [],
      response: [{ id: 1, title: 'Test Todo', completed: false }],
    },
  ];

  const { getByText } = render(
    <DataProvider>
      <MockResolver fixtures={fixtures}>
        <TodoList />
      </MockResolver>
    </DataProvider>,
  );

  expect(getByText('Test Todo')).toBeInTheDocument();
});

Testing with nock (HTTP Endpoint Testing)

import nock from 'nock';

it('should fetch data from API', async () => {
  const scope = nock('https://jsonplaceholder.typicode.com')
    .get('/todos/1')
    .reply(200, { id: 1, title: 'Test', completed: false });

  const result = await TodoResource.get({ id: 1 });
  
  expect(result.title).toBe('Test');
  scope.done();
});

Testing Managers

it('should handle manager middleware', async () => {
  const mockManager = {
    middleware: (controller) => (next) => async (action) => {
      if (action.type === 'FETCH') {
        console.log('Fetch action:', action);
      }
      return next(action);
    },
    cleanup: jest.fn(),
  };

  const { controller } = renderDataHook(
    () => useController(),
    { managers: [mockManager] },
  );

  await controller.fetch(TodoResource.get, { id: 1 });
  expect(mockManager.cleanup).not.toHaveBeenCalled();
});

Test File Organization

Keep tests under packages/*/src/**/__tests__:

packages/react/src/hooks/__tests__/useSuspense.test.ts
packages/react/src/components/__tests__/DataProvider.test.tsx

Test naming:

• Node-only: *.node.test.ts[x]
• React Native: *.native.test.ts[x]
• Regular: *.test.ts[x]

Best Practices

• Use renderDataHook() for testing hooks that use @data-client/react hooks
• Use fixtures or interceptors when testing hooks or components
• Use nock when testing networking definitions
• Test both success and error scenarios
• Test mutations and their side effects
• Don't mock @data-client internals directly
• Don't use raw fetch in tests when fixtures are available
• Don't manually call renderDataHook.cleanup() in afterEach -- cleanup is automatic

References

For detailed API documentation, see the references directory:

• renderDataHook - Hook testing utility
• makeRenderDataHook - Custom hook renderer
• Fixtures - Fixture format reference
• MockResolver - Component testing wrapper
• mockInitialState - Create initial state
• unit-testing-hooks - Hook testing guide
• unit-testing-components - Component testing guide