Vitest Prisma Dual Query Mocking

Problem

When code uses both findFirst and findUnique on the same Prisma/ZenStack model, a single mock implementation doesn't work correctly. One query returns the mocked data while the other returns undefined, causing test failures.

Context / Trigger Conditions

• Test error: "Cannot read properties of undefined (reading 'value')" or similar
• Code uses db.model.findFirst({ where: {...} }) for one query
• Code uses db.model.findUnique({ where: { composite_key: {...} } }) for another query
• Both queries target the same model (e.g., userPreference)
• Single mock like mockDb.model.findFirst = vi.fn().mockResolvedValue(data) doesn't cover both
• Tests pass individually but fail when both queries run in same test