How to get AI to write tests automatically

Work strictly on TDD:
1. Write ALL tests for this function/class.
2. Tests should cover:
   - happy path
   edge cases (empty lines, null, maximum values)
   - errors and exceptions
   integration with external services (with mocks)

Use Vitest + @testing-library + vi.fn() for moks.

Structure:
-   tests   /filename.test.ts
- mocks/ for external APIs

First, show only the tests (without implementing the function). Then I'll say "implement.".

Create tests with 100% twig coverage.

Definitely:
Close all external calls (Claude API, Supabase, Telegram Bot API, n8n, etc.)
- Use vi.mock()/jest.mock()
- Add retry logic tests and timeouts
Check that errors are logged correctly
Add snapshot tests for UI components (if Next.js)

Save Moki in a separate folder   mocks  .

Now create a separate file integration.test.ts

Requirements:
Run a real database (Supabase test instance or Docker Postgres)
Test Full Flow: From Telegram Message to Response
Use testcontainers or supabase-test-utils
Add beforeAll/afterAll to clean up data

1. Write the tests.
2. Run the command `npm run test` (or `vitest`).
3. If you fall, automatically correct the code or tests until everything passes.
4. At the end, show the cover report (coverage).

Go through the project and create the missing .test.ts files for each feature and component.

Priority:
1. handlers/
2. services/
3. repositories
4. utils/

First, show a list of files that will be created.

Get ready for GitHub Actions:

- Add workflow .github/workflows/test.yml
Tests must work in CI (no real Telegram token)
Add coverage threshold 85%
- Drop the build if the cover is lower

For each test, add a detailed description/it with a description in Russian:
- What we're testing.
- Conditions
- Expected outcome
- Why is the test important

The goal is to create a complete test base for the code provided.

Apply in order:
1. TDD (tests first)
2. 100% branching
3. Full of external services
4. Unit + Integration tests
5. Snapshot tests where necessary
6. Automatic start + error correction
7. GitHub Actions workflow
8. Coverage report + recommendations for improvement

Upon completion:
- Show the folder structure   tests
- Give the launch command
- Show me an example of the coverage report
- Add comments // TODO: for complex cases

// services/subscriptionService.ts
export async function activateSubscription(userId: string, plan: string) { ... }