Feature: Add Comprehensive Unit Test Coverage for Common Utilities and Hooks

src/common/hooks/__tests__/useCacheResponse.test.ts

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+import { renderHook } from '@testing-library/react';
+import useCacheResponse from '../useCacheResponse';
+
+describe('useCacheResponse', () => {
+  it('stores and retrieves cached data', () => {
+    const { result } = renderHook(() => useCacheResponse());
+    const [retrieveCache, createCache] = result.current;
+
+    createCache('testKey', { data: 'hello' });
+    expect(retrieveCache('testKey')).toEqual({ data: 'hello' });
+  });
+
+  it('returns null for a cache key that does not exist', () => {
+    const { result } = renderHook(() => useCacheResponse());
+    const [retrieveCache] = result.current;
+
+    expect(retrieveCache('nonExistentKey')).toBeNull();
+  });
+
+  it('overwrites existing cache entries', () => {
+    const { result } = renderHook(() => useCacheResponse());
+    const [retrieveCache, createCache] = result.current;
+
+    createCache('key', 'first');
+    createCache('key', 'second');
+    expect(retrieveCache('key')).toBe('second');
+  });
+
+  it('supports different data types', () => {
+    const { result } = renderHook(() => useCacheResponse());
+    const [retrieveCache, createCache] = result.current;
+
+    createCache('number', 42);
+    createCache('array', [1, 2, 3]);
+    createCache('null', null);
+
+    expect(retrieveCache('number')).toBe(42);
+    expect(retrieveCache('array')).toEqual([1, 2, 3]);
+    // null is falsy, so the hook returns null for it too
+    expect(retrieveCache('null')).toBeNull();
+  });
+});

src/common/hooks/__tests__/useContributors.test.js

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+import { renderHook, waitFor } from '@testing-library/react';
+import useContributors from '../useContributors';
+
+beforeEach(() => {
+  global.fetch = jest.fn();
+  process.env.REACT_APP_PLAY_API_URL = 'https://api.test.com';
+});
+
+afterEach(() => {
+  jest.restoreAllMocks();
+  delete process.env.REACT_APP_PLAY_API_URL;
+});
+
+const mockContributors = [
+  { login: 'user1', type: 'User', contributions: 50 },
+  { login: 'dependabot', type: 'Bot', contributions: 100 },
+  { login: 'user2', type: 'User', contributions: 30 },
+  { login: 'user3', type: 'User', contributions: 80 }
+];
+
+describe('useContributors', () => {
+  it('fetches contributors and filters out bots', async () => {
+    global.fetch.mockResolvedValueOnce({
+      json: () => Promise.resolve(mockContributors)
+    });
+
+    const { result } = renderHook(() => useContributors(false));
+
+    expect(result.current.isLoading).toBe(true);
+
+    await waitFor(() => {
+      expect(result.current.isLoading).toBe(false);
+    });
+
+    expect(result.current.data).toHaveLength(3);
+    expect(result.current.data.every((c) => c.type !== 'Bot')).toBe(true);
+    expect(result.current.error).toBeUndefined();
+  });
+
+  it('sorts contributors by contributions when sorted=true', async () => {
+    global.fetch.mockResolvedValueOnce({
+      json: () => Promise.resolve(mockContributors)
+    });
+
+    const { result } = renderHook(() => useContributors(true));
+
+    await waitFor(() => {
+      expect(result.current.isLoading).toBe(false);
+    });
+
+    const contributions = result.current.data.map((c) => c.contributions);
+    expect(contributions).toEqual([80, 50, 30]); // descending order, bot excluded
+  });
+
+  it('sets error on fetch failure', async () => {
+    const mockError = new Error('Network error');
+    global.fetch.mockRejectedValueOnce(mockError);
+
+    const { result } = renderHook(() => useContributors(false));
+
+    await waitFor(() => {
+      expect(result.current.isLoading).toBe(false);
+    });
+
+    expect(result.current.error).toBe(mockError);
+    expect(result.current.data).toBeUndefined();
+  });
+
+  it('fetches from the correct API URL', async () => {
+    global.fetch.mockResolvedValueOnce({
+      json: () => Promise.resolve([])
+    });
+
+    renderHook(() => useContributors(false));
+
+    expect(global.fetch).toHaveBeenCalledWith('https://api.test.com/react-play/contributors');
+  });
+});

src/common/hooks/__tests__/useFeaturedPlays.test.js

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+import { renderHook, waitFor } from '@testing-library/react';
+import useFeaturedPlays from '../useFeaturedPlays';
+import { submit } from 'common/services/request';
+
+// Mock the services/request module
+jest.mock('common/services/request', () => ({
+  submit: jest.fn()
+}));
+
+jest.mock('common/services/request/query/fetch-plays-filter', () => ({
+  FetchPlaysFilter: {
+    getAllFeaturedPlays: jest.fn(() => 'mock-query')
+  }
+}));
+
+describe('useFeaturedPlays', () => {
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('returns featured plays data on success', async () => {
+    const mockPlays = [
+      { id: 1, name: 'Play 1' },
+      { id: 2, name: 'Play 2' }
+    ];
+    submit.mockResolvedValueOnce(mockPlays);
+
+    const { result } = renderHook(() => useFeaturedPlays());
+
+    // [loading, error, data]
+    expect(result.current[0]).toBe(true); // loading
+
+    await waitFor(() => {
+      expect(result.current[0]).toBe(false); // loading done
+    });
+
+    expect(result.current[1]).toBeNull(); // no error
+    expect(result.current[2]).toEqual(mockPlays); // data
+  });
+
+  it('sets error on failure', async () => {
+    const mockError = { message: 'GraphQL error' };
+    submit.mockRejectedValueOnce([mockError]);
+
+    const { result } = renderHook(() => useFeaturedPlays());
+
+    await waitFor(() => {
+      expect(result.current[0]).toBe(false);
+    });
+
+    expect(result.current[1]).toEqual(mockError); // error
+  });
+});

src/common/hooks/__tests__/useFetch.test.js

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+import { renderHook, waitFor } from '@testing-library/react';
+import useFetch from '../useFetch';
+
+// Mock global fetch
+beforeEach(() => {
+  global.fetch = jest.fn();
+});
+
+afterEach(() => {
+  jest.restoreAllMocks();
+});
+
+describe('useFetch', () => {
+  it('returns data on successful fetch', async () => {
+    const mockData = [{ id: 1, name: 'Play 1' }];
+    global.fetch.mockResolvedValueOnce({
+      json: () => Promise.resolve(mockData)
+    });
+
+    const { result } = renderHook(() => useFetch('https://api.example.com/data'));
+
+    // Initially loading
+    expect(result.current.loading).toBe(true);
+    expect(result.current.data).toEqual([]);
+
+    await waitFor(() => {
+      expect(result.current.loading).toBe(false);
+    });
+
+    expect(result.current.data).toEqual(mockData);
+    expect(result.current.error).toBeNull();
+  });
+
+  it('sets error on fetch failure', async () => {
+    const mockError = new Error('Network error');
+    global.fetch.mockRejectedValueOnce(mockError);
+
+    const { result } = renderHook(() => useFetch('https://api.example.com/fail'));
+
+    await waitFor(() => {
+      expect(result.current.loading).toBe(false);
+    });
+
+    expect(result.current.error).toBe(mockError);
+    expect(result.current.data).toEqual([]);
+  });
+
+  it('passes options to fetch', async () => {
+    global.fetch.mockResolvedValueOnce({
+      json: () => Promise.resolve({})
+    });
+
+    const options = { method: 'POST', body: JSON.stringify({ test: true }) };
+    renderHook(() => useFetch('https://api.example.com/data', options));
+
+    expect(global.fetch).toHaveBeenCalledWith('https://api.example.com/data', options);
+  });
+});

src/common/hooks/__tests__/useGitHub.test.js

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+import { renderHook, waitFor } from '@testing-library/react';
+import useGitHub from '../useGitHub';
+
+beforeEach(() => {
+  global.fetch = jest.fn();
+});
+
+afterEach(() => {
+  jest.restoreAllMocks();
+});
+
+describe('useGitHub', () => {
+  it('fetches GitHub user data successfully', async () => {
+    const mockUser = {
+      login: 'octocat',
+      name: 'The Octocat',
+      public_repos: 8
+    };
+    global.fetch.mockResolvedValueOnce({
+      json: () => Promise.resolve(mockUser)
+    });
+
+    const { result } = renderHook(() => useGitHub('octocat'));
+
+    expect(result.current.isLoading).toBe(true);
+
+    await waitFor(() => {
+      expect(result.current.isLoading).toBe(false);
+    });
+
+    expect(result.current.data).toEqual(mockUser);
+    expect(result.current.error).toBeUndefined();
+    expect(global.fetch).toHaveBeenCalledWith('https://api.github.com/users/octocat');
+  });
+
+  it('handles fetch errors', async () => {
+    const mockError = new Error('Rate limited');
+    global.fetch.mockRejectedValueOnce(mockError);
+
+    const { result } = renderHook(() => useGitHub('unknown-user'));
+
+    await waitFor(() => {
+      expect(result.current.isLoading).toBe(false);
+    });
+
+    expect(result.current.error).toBe(mockError);
+    expect(result.current.data).toBeUndefined();
+  });
+});

src/common/hooks/__tests__/useLikePlays.test.js

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+import { renderHook } from '@testing-library/react';
+import useLikePlays from '../useLikePlays';
+import { submit } from 'common/services/request';
+
+jest.mock('common/services/request', () => ({
+  submit: jest.fn()
+}));
+
+jest.mock('common/services/request/query/like-play', () => ({
+  likeIndividualPlay: jest.fn((obj) => ({ type: 'LIKE', ...obj })),
+  unlikeIndividualPlay: jest.fn((obj) => ({ type: 'UNLIKE', ...obj }))
+}));
+
+describe('useLikePlays', () => {
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('likePlay calls submit and resolves on success', async () => {
+    const mockResponse = { id: 1, liked: true };
+    submit.mockResolvedValueOnce(mockResponse);
+
+    const { result } = renderHook(() => useLikePlays());
+    const response = await result.current.likePlay({ play_id: 'abc' });
+
+    expect(response).toEqual(mockResponse);
+    expect(submit).toHaveBeenCalledTimes(1);
+  });
+
+  it('likePlay rejects on submit failure', async () => {
+    const mockError = new Error('Mutation failed');
+    submit.mockRejectedValueOnce(mockError);
+
+    const { result } = renderHook(() => useLikePlays());
+
+    await expect(result.current.likePlay({ play_id: 'abc' })).rejects.toThrow('Mutation failed');
+  });
+
+  it('unLikePlay calls submit and resolves on success', async () => {
+    const mockResponse = { id: 1, liked: false };
+    submit.mockResolvedValueOnce(mockResponse);
+
+    const { result } = renderHook(() => useLikePlays());
+    const response = await result.current.unLikePlay({ play_id: 'abc' });
+
+    expect(response).toEqual(mockResponse);
+  });
+
+  it('unLikePlay rejects on submit failure', async () => {
+    submit.mockRejectedValueOnce(new Error('Delete failed'));
+
+    const { result } = renderHook(() => useLikePlays());
+
+    await expect(result.current.unLikePlay({ play_id: 'abc' })).rejects.toThrow('Delete failed');
+  });
+});