sugarr/test/core/langfuse/PromptService.test.ts

import { describe, expect, it, vi } from 'vitest';
import { PromptService } from '../../../src/core/langfuse/PromptService';
import type { PromptFetcher, RawPrompt } from '../../../src/core/langfuse/PromptGateway';

function makeRawPrompt(name: string, version = 1): RawPrompt {
  return {
    name,
    version,
    config: { model: 'gpt-4o-mini' },
    compile: (variables) => [{ role: 'user', content: `hello ${String(variables.who)}` }],
  };
}

describe('PromptService', () => {
  it('fetches once and reuses the cache on subsequent calls when caching is enabled', async () => {
    const fetch = vi.fn().mockResolvedValue(makeRawPrompt('greet'));
    const fetcher: PromptFetcher = { fetch };
    const service = new PromptService(fetcher, true);

    await service.getCompiled('greet', { who: 'a' });
    const compiled = await service.getCompiled('greet', { who: 'b' });

    expect(fetch).toHaveBeenCalledTimes(1);
    expect(compiled.messages).toEqual([{ role: 'user', content: 'hello b' }]);
    expect(compiled.config).toEqual({ model: 'gpt-4o-mini' });
  });

  it('always refetches when caching is disabled', async () => {
    const fetch = vi.fn().mockResolvedValue(makeRawPrompt('greet'));
    const fetcher: PromptFetcher = { fetch };
    const service = new PromptService(fetcher, false);

    await service.getCompiled('greet', { who: 'a' });
    await service.getCompiled('greet', { who: 'b' });

    expect(fetch).toHaveBeenCalledTimes(2);
  });

  it('invalidate(name) forces a refetch for that name only', async () => {
    const fetch = vi.fn().mockResolvedValue(makeRawPrompt('greet'));
    const fetcher: PromptFetcher = { fetch };
    const service = new PromptService(fetcher, true);

    await service.getCompiled('greet', {});
    service.invalidate('greet');
    await service.getCompiled('greet', {});

    expect(fetch).toHaveBeenCalledTimes(2);
  });

  it('invalidate() with no name clears the whole cache', async () => {
    const fetch = vi.fn().mockImplementation((name: string) => Promise.resolve(makeRawPrompt(name)));
    const fetcher: PromptFetcher = { fetch };
    const service = new PromptService(fetcher, true);

    await service.getCompiled('a', {});
    await service.getCompiled('b', {});
    service.invalidate();
    await service.getCompiled('a', {});
    await service.getCompiled('b', {});

    expect(fetch).toHaveBeenCalledTimes(4);
  });
});