Testing ComuniTEA: Jest, jest-expo, and Smoke Tests

ComuniTEA’s test suite uses Jest with the jest-expo preset and React Native Testing Library to verify that core modules initialize correctly and that the application’s data contracts are sound. The current suite focuses on smoke tests — fast, low-overhead tests that confirm modules load without errors and export the values and shapes expected by the rest of the app. The suite is designed to grow incrementally with the project; new feature tests slot directly into the existing configuration without any setup changes.

Test Framework

Tool	Version	Role
`jest`	^29.7.0	Test runner
`jest-expo`	~57.0.2	Expo-aware Jest preset — handles Metro transforms and native mocks
`@testing-library/react-native`	^13.3.3	Component and hook testing utilities
`react-test-renderer`	19.0.0	Required peer for React Native Testing Library
`@types/jest`	^29.5.14	TypeScript types for `describe`, `it`, `expect`, etc.

The Jest configuration lives directly in package.json under the "jest" key:

"jest": {
  "preset": "jest-expo",
  "testMatch": [
    "**/__tests__/**/*.test.{ts,tsx}"
  ],
  "transformIgnorePatterns": [
    "node_modules/(?!((jest-)?react-native|@react-native(-community)?)|expo(nent)?|@expo(nent)?/.*|@expo-google-fonts/.*|react-navigation|@react-navigation/.*|@unimodules/.*|unimodules|sentry-expo|native-base|react-native-svg|lucide-react-native)"
  ],
  "moduleNameMapper": {
    "^@/(.*)$": "<rootDir>/$1",
    "^react-native-reanimated$": "<rootDir>/node_modules/react-native-reanimated/mock",
    "^react-native-worklets(.*)$": "<rootDir>/__mocks__/react-native-worklets.js"
  },
  "setupFilesAfterEnv": []
}

Running Tests

Run the full test suite

npm test

Runs all files matching **/__tests__/**/*.test.{ts,tsx}. Exits with code 0 even if no tests are discovered (see the --passWithNoTests note below).

Run in watch mode

npm run test:watch

Starts Jest in interactive watch mode. Re-runs affected tests on every file save. Ideal for TDD workflows.

The test script uses the --passWithNoTests flag: jest --passWithNoTests. This is intentional — the test suite starts minimal and expands alongside the project. CI pipelines will not fail on a fresh branch that hasn’t added tests yet.

Module Mocks

React Native’s native modules are not available in the Node.js environment that Jest runs in. ComuniTEA handles this at two levels.

Built-in Reanimated Mock

react-native-reanimated ships an official Jest mock. The moduleNameMapper points to it directly:

"^react-native-reanimated$": "<rootDir>/node_modules/react-native-reanimated/mock"

Worklets Mock

react-native-worklets (a peer dependency of Reanimated 4) has no built-in mock and will crash Jest with a native module error. A manual mock is provided at __mocks__/react-native-worklets.js:

"^react-native-worklets(.*)$": "<rootDir>/__mocks__/react-native-worklets.js"

Babel Config — Reanimated Disabled in Tests

babel.config.js disables the Reanimated Babel plugin when NODE_ENV=test, preventing the worklets transform from running during the Jest pass:

// babel.config.js
module.exports = function (api) {
    api.cache.using(() => process.env.NODE_ENV);
    const isTest = process.env.NODE_ENV === 'test';

    return {
        presets: [
            [
                'babel-preset-expo',
                {
                    // The reanimated plugin requires react-native-worklets
                    // which is not available in the Jest (pure Node.js) environment.
                    reanimated: !isTest,
                },
            ],
        ],
    };
};

Per-Test Native Module Mocks

Tests that import modules with native dependencies declare jest.mock() calls at the top of the file. The smoke test file demonstrates the full set of mocks required to load the Supabase client and audio subsystem:

jest.mock('@react-native-async-storage/async-storage', () =>
    require('@react-native-async-storage/async-storage/jest/async-storage-mock')
);
jest.mock('@react-native-community/netinfo', () => ({
    fetch: jest.fn().mockResolvedValue({ isConnected: true, isInternetReachable: true }),
    addEventListener: jest.fn(() => jest.fn()),
}));
jest.mock('react-native-url-polyfill/auto', () => {});
jest.mock('expo-speech', () => ({ speak: jest.fn(), stop: jest.fn() }));
jest.mock('expo-audio', () => ({
    createAudioPlayer: jest.fn(() => ({
        remove: jest.fn(),
        play: jest.fn(),
        pause: jest.fn(),
        addListener: jest.fn(() => ({ remove: jest.fn() })),
    })),
    setAudioModeAsync: jest.fn(),
}));
jest.mock('expo-file-system/legacy', () => ({
    documentDirectory: '/tmp/',
    cacheDirectory: '/tmp/',
    writeAsStringAsync: jest.fn().mockResolvedValue(undefined),
    deleteAsync: jest.fn().mockResolvedValue(undefined),
    readAsStringAsync: jest.fn().mockResolvedValue(''),
    EncodingType: { Base64: 'base64' },
}));

Path Aliases in Tests

The moduleNameMapper in the Jest config maps the @/ prefix for test imports, alongside native module mocks:

"moduleNameMapper": {
  "^@/(.*)$": "<rootDir>/$1",
  "^react-native-reanimated$": "<rootDir>/node_modules/react-native-reanimated/mock",
  "^react-native-worklets(.*)$": "<rootDir>/__mocks__/react-native-worklets.js"
}

This means require('@/lib/supabase') inside a test file resolves to <rootDir>/lib/supabase. Note that the Jest ^@/(.*)$ mapper uses a different prefix convention from the TypeScript path aliases in tsconfig.json (@lib/*, @features/*, etc.), which are resolved by the Metro bundler and TypeScript compiler but not by Jest. In test files, use the @/ prefix or relative paths (e.g., ../../lib/supabase) to ensure correct resolution. No separate Babel plugin or Jest transform is needed for this mapper.

Transform Ignore Patterns

By default Jest does not transform node_modules. ComuniTEA’s transformIgnorePatterns opts several packages back into the Babel transform pipeline because they ship ES module or JSX source that Node.js cannot execute natively:

node_modules/(?!((jest-)?react-native|@react-native(-community)?)|expo(nent)?|@expo(nent)?/.*|@expo-google-fonts/.*|react-navigation|@react-navigation/.*|@unimodules/.*|unimodules|sentry-expo|native-base|react-native-svg|lucide-react-native)

Packages that are transformed (whitelisted from the ignore pattern):

Package group	Reason
`react-native`, `jest-react-native`	Core RN source ships untransformed JSX
`@react-native(-community)?`	Community modules use JSX/ESM
`expo`, `expo-`, `@expo/`, `@expo-google-fonts/*`	Expo packages use JSX and ESM syntax
`react-navigation`, `@react-navigation/*`	Uses JSX
`lucide-react-native`	Ships ESM icons
`react-native-svg`, `native-base`	JSX source

Smoke Tests

The first test suite lives at __tests__/smoke/core.test.ts — Phase 0 smoke tests that verify the core modules load and export valid data shapes.

// __tests__/smoke/core.test.ts

describe('Smoke tests — módulos core', () => {

  it('supabase client se inicializa correctamente con variables de entorno', () => {
      const { supabase } = require('../../lib/supabase');
      expect(supabase).toBeDefined();
      expect(typeof supabase.from).toBe('function');
      expect(typeof supabase.auth).toBe('object');
  });

  it('constantes de vocabulario exportan datos válidos', () => {
      const { VOCABULARY } = require('../../constants/Vocabulary');
      expect(typeof VOCABULARY).toBe('object');
      expect(Object.keys(VOCABULARY).length).toBeGreaterThan(0);
      // Each category must have at least one item with id and label
      const firstKey = Object.keys(VOCABULARY)[0];
      const firstItem = VOCABULARY[firstKey][0];
      expect(typeof firstItem.id).toBe('string');
      expect(typeof firstItem.label).toBe('string');
  });

  it('constantes de categorías exportan datos válidos', () => {
      const { BASIC_CATEGORIES } = require('../../constants/Categories');
      expect(Array.isArray(BASIC_CATEGORIES)).toBe(true);
      expect(BASIC_CATEGORIES.length).toBeGreaterThan(0);
      const first = BASIC_CATEGORIES[0];
      expect(typeof first.id).toBe('string');
      expect(typeof first.label).toBe('string');
  });

  it('supabase.ts lanza error sin variables de entorno', () => {
      const original_url = process.env.EXPO_PUBLIC_SUPABASE_URL;
      const original_key = process.env.EXPO_PUBLIC_SUPABASE_ANON_KEY;

      delete process.env.EXPO_PUBLIC_SUPABASE_URL;
      delete process.env.EXPO_PUBLIC_SUPABASE_ANON_KEY;

      // Limpiar el módulo en caché para forzar re-ejecución
      jest.resetModules();

      expect(() => {
          require('../../lib/supabase');
      }).toThrow('[ComuniTEA]');

      // Restaurar
      process.env.EXPO_PUBLIC_SUPABASE_URL = original_url;
      process.env.EXPO_PUBLIC_SUPABASE_ANON_KEY = original_key;
      jest.resetModules();
  });

});

The four smoke tests cover:

Supabase Client Initialization

Verifies that lib/supabase exports a valid Supabase client with .from() and .auth when EXPO_PUBLIC_SUPABASE_URL and EXPO_PUBLIC_SUPABASE_ANON_KEY are present in the environment.

Vocabulary Constants

Confirms that constants/Vocabulary.ts exports a non-empty VOCABULARY object where each entry contains at least one item with string id and label fields.

Category Constants

Confirms that constants/Categories.ts exports a non-empty BASIC_CATEGORIES array where each element has string id and label fields.

Missing Env Var Guard

Verifies that lib/supabase throws an error prefixed with [ComuniTEA] when the Supabase environment variables are absent, catching misconfigured deployments at startup.

Environment variables for the Supabase client are set at the top of the test file before any require() calls:

process.env.EXPO_PUBLIC_SUPABASE_URL = 'https://test.supabase.co';
process.env.EXPO_PUBLIC_SUPABASE_ANON_KEY = 'test-anon-key';

TypeScript in Tests

All test files use .ts / .tsx extensions and are fully type-checked by @types/jest. The jest-expo preset wires up the necessary TypeScript transform through Babel. The tsconfig.json include glob (**/*.ts, **/*.tsx) covers the __tests__/ directory automatically — no extra tsconfig entry is needed for test files.

Testing Guidelines for Contributors

Where to Place Test Files

All tests live under __tests__/ and must match the pattern **/*.test.{ts,tsx}:

__tests__/
├── smoke/
│   └── core.test.ts        # Phase 0 smoke tests
├── components/             # Component tests (React Native Testing Library)
│   └── ActionGridItem.test.tsx
├── hooks/                  # Hook tests (renderHook)
│   └── useSpeech.test.ts
└── stores/                 # Zustand store tests
    └── appThemeStore.test.ts

Mocking Supabase Calls

For feature tests that involve Supabase queries, mock the client at the module level so tests are fast and deterministic:

jest.mock('../../lib/supabase', () => ({
    supabase: {
        from: jest.fn(() => ({
            select: jest.fn().mockReturnThis(),
            eq: jest.fn().mockReturnThis(),
            single: jest.fn().mockResolvedValue({ data: { id: '1' }, error: null }),
        })),
        auth: {
            getUser: jest.fn().mockResolvedValue({ data: { user: null }, error: null }),
        },
    },
}));

Testing Hooks with React Native Testing Library

Use renderHook from @testing-library/react-native to test custom hooks in isolation:

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

it('useSpeech initializes without crashing', () => {
    const { result } = renderHook(() => useSpeech());
    expect(result.current).toBeDefined();
});

Testing Zustand Stores

Reset Zustand store state between tests to avoid cross-test pollution:

import { appThemeStore } from '../../stores/appThemeStore';

beforeEach(() => {
    appThemeStore.setState({ theme: 'sage' });
});

it('theme switches to rojo', () => {
    act(() => appThemeStore.getState().setTheme('rojo'));
    expect(appThemeStore.getState().theme).toBe('rojo');
});

Because babel.config.js disables the Reanimated transform when NODE_ENV=test, any component that uses useAnimatedStyle or useSharedValue will work with the mock provided by moduleNameMapper without any additional setup in individual test files.

Data & State

Feature Modules

Development

Testing ComuniTEA: Jest, jest-expo, and Smoke Tests

Test Framework

Running Tests

Module Mocks

Built-in Reanimated Mock

Worklets Mock

Babel Config — Reanimated Disabled in Tests

Per-Test Native Module Mocks

Path Aliases in Tests

Transform Ignore Patterns

Smoke Tests

Supabase Client Initialization

Vocabulary Constants

Category Constants

Missing Env Var Guard

TypeScript in Tests

Testing Guidelines for Contributors

Where to Place Test Files

Mocking Supabase Calls

Testing Hooks with React Native Testing Library

Testing Zustand Stores

Build docs developers (and LLMs) love

Data & State

Feature Modules

Development

Documentation Index

​Test Framework

​Running Tests

​Module Mocks

​Built-in Reanimated Mock

​Worklets Mock

​Babel Config — Reanimated Disabled in Tests

​Per-Test Native Module Mocks

​Path Aliases in Tests

​Transform Ignore Patterns

​Smoke Tests

Supabase Client Initialization

Vocabulary Constants

Category Constants

Missing Env Var Guard

​TypeScript in Tests

​Testing Guidelines for Contributors

​Where to Place Test Files

​Mocking Supabase Calls

​Testing Hooks with React Native Testing Library

​Testing Zustand Stores

Build docs developers (and LLMs) love

Test Framework

Running Tests

Module Mocks

Built-in Reanimated Mock

Worklets Mock

Babel Config — Reanimated Disabled in Tests

Per-Test Native Module Mocks

Path Aliases in Tests

Transform Ignore Patterns

Smoke Tests

TypeScript in Tests

Testing Guidelines for Contributors

Where to Place Test Files

Mocking Supabase Calls

Testing Hooks with React Native Testing Library

Testing Zustand Stores