Testing Guidelines

Principles

• •Test behavior, not implementation
• •Avoid brittle tests — do not test internal state
• •Mock only external dependencies (API, storage)

Selectors (Testing Library)

Priority order:

1. •getByRole — native accessibility
2. •getByLabelText — forms
3. •getByPlaceholderText — inputs
4. •getByText — text content
5. •getByTestId — last resort

Test Structure

describe('UserCard', () => {
  it('should display user name and trigger edit on button click', async () => {
    // Arrange
    const onEdit = vi.fn();
    render(<UserCard name="John" onEdit={onEdit} />);

    // Act
    await userEvent.click(screen.getByRole('button', { name: /edit/i }));

    // Assert
    expect(screen.getByText('John')).toBeInTheDocument();
    expect(onEdit).toHaveBeenCalledOnce();
  });
});

Test Doubles

• •Fake — Simplified implementation (in-memory repository)
• •Stub — Returns predefined values
• •Mock — Verifies calls (use sparingly)

Coverage

• •Target 70%+ on critical business logic (domain)
• •Do not aim for 100% — superficial tests have little value