Testing Server Actions

For Vitest mocking patterns (vi.mock(), vi.fn(), mockResolvedValue), see vitest-4/skills/writing-vitest-tests/SKILL.md.

Basic Server Action Test

import { submitContact } from './actions';

test('submitContact validates email', async () => {
  const formData = new FormData();
  formData.set('email', 'invalid');
  formData.set('message', 'Hello');

  const result = await submitContact(null, formData);

  expect(result.error).toBeTruthy();
});

test('submitContact succeeds with valid data', async () => {
  const formData = new FormData();
  formData.set('email', 'test@example.com');
  formData.set('message', 'Hello');

  const result = await submitContact(null, formData);

  expect(result.success).toBe(true);
});

Mocking Database Calls

import { createUser } from './actions';
import { db } from './db';

vi.mock('./db', () => ({
  db: {
    users: {
      create: vi.fn(),
    },
  },
}));

test('createUser creates database record', async () => {
  db.users.create.mockResolvedValue({ id: '123', name: 'Alice' });

  const formData = new FormData();
  formData.set('name', 'Alice');
  formData.set('email', 'alice@example.com');

  const result = await createUser(null, formData);

  expect(db.users.create).toHaveBeenCalledWith({
    name: 'Alice',
    email: 'alice@example.com',
  });

  expect(result.success).toBe(true);
  expect(result.userId).toBe('123');
});

Testing with Authentication

import { deletePost } from './actions';
import { getSession } from './auth';

vi.mock('./auth');

test('deletePost requires authentication', async () => {
  getSession.mockResolvedValue(null);

  await expect(deletePost('post-123')).rejects.toThrow('Unauthorized');
});

test('deletePost checks ownership', async () => {
  getSession.mockResolvedValue({ user: { id: 'user-1' } });

  await expect(deletePost('post-owned-by-user-2')).rejects.toThrow('Forbidden');
});

For comprehensive Server Action testing, test the function directly in isolation.

References

• @vitest-4/skills/writing-vitest-tests – Mocking and spy patterns