When a mock server helps
Use a mock server when local fixtures are no longer enough. If several developers, test suites, or demos need the same response, a hosted mock URL is easier to share than a file inside one repository.
Define one scenario per response: successful creation, validation failure, expired session, missing record, slow dependency, and unexpected server error. Clear scenario names make mocks easy to use in bug reports and design reviews.
GET /api/report
200 dashboard-ready
GET /api/report
500 analytics-provider-down