npm install --save-dev @growthbook/growthbook

import { GrowthBookClient } from '@growthbook/growthbook';

const gbClient = new GrowthBookClient().initSync({
  payload: {
    features: {
      'show-new-ui': { defaultValue: true },
      'experiment-x': {
        defaultValue: false,
        rules: [{ condition: { id: 'test-user-1' }, force: true }],
      },
    },
  },
});

test('flag on', () => {
  const userContext = { attributes: { id: 'user-1' } };
  expect(gbClient.isOn('show-new-ui', userContext)).toBe(true);
});

test('typed feature value', () => {
  const userContext = { attributes: { id: 'user-1' } };
  const color = gbClient.getFeatureValue('button-color', 'blue', userContext);
  expect(['blue', 'red', 'green']).toContain(color);
});

test('user-specific evaluation', () => {
  const instance = gbClient.createScopedInstance({
    attributes: { id: 'user-1', plan: 'premium' },
  });
  expect(instance.isOn('premium-feature')).toBe(true);
});

test('inline experiment returns one variant', () => {
  const userContext = { attributes: { id: 'user-1' } };
  const { value } = gbClient.runInlineExperiment({
    key: 'my-experiment',
    variations: ['red', 'blue', 'green'],
    coverage: 1.0,
    weights: [0.33, 0.34, 0.33],
  }, userContext);
  expect(['red', 'blue', 'green']).toContain(value);
});

test('experiment tracking fires', () => {
  const tracked: any[] = [];
  const client = new GrowthBookClient({
    trackingCallback: (exp, result, ctx) => {
      tracked.push({ key: exp.key, variation: result.key });
    },
  }).initSync({ payload: {} });

  client.runInlineExperiment(
    { key: 'exp-x', variations: [0, 1] },
    { attributes: { id: 'user-1' } }
  );

  expect(tracked).toHaveLength(1);
  expect(tracked[0].key).toBe('exp-x');
});

const evaluated: any[] = [];

test('feature usage logged', () => {
  const userContext = {
    attributes: { id: 'user-1' },
    onFeatureUsage: (key: string, result: any) => {
      evaluated.push({ key, value: result.value });
    },
  };

  gbClient.evalFeature('feature-x', userContext);
  expect(evaluated).toContainEqual(expect.objectContaining({ key: 'feature-x' }));
});

interface AppFeatures {
  'button-color': string;
  'font-size': number;
  'newForm': boolean;
}

const gbClient = new GrowthBookClient<AppFeatures>({}).initSync({ payload: {} });

const color = gbClient.getFeatureValue('button-color', 'blue', ctx);  // typed
// gbClient.isOn('buton-color', ctx);  // typo → compile error

npm test

jobs:
  growthbook-tests:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v5
      - uses: actions/setup-node@v4
      - run: npm ci && npm test