DEV Community
•
2026-04-19 23:37
DI + Fake + in-memory: Writing Frontend Tests That Survive Refactors
Originally published at recca0120.github.io
The most common testing pattern I see looks like this:
test('saves user data', () => {
const mockStorage = {
set: vi.fn(),
get: vi.fn().mockReturnValue(null),
};
const service = new UserService(mockStorage);
service.save({ id: 1, name: 'Alice' });
expect(mockStorage.set).toHaveBeenCalledWith('user:1', { id: 1, name: 'Alice' });...
