Repository Integration Tests with PostgreSQL Volume 07 - Advanced Application Architecture | Phase 24
Test the real adapter separately The concrete Prisma repository should be tested against a real disposable/resettable PostgreSQL database because its job is to translate the contract into real persistence behavior. Current Prisma guidance explicitly distinguishes unit tests with mocks from integration tests against a real test database.
Integration scope • Apply migrations to a test database.
• Seed the minimum Workspace/User/Membership/Project graph.
• Call PrismaTaskRepository directly.
• Verify scoped reads cannot cross Workspaces.
• Verify pagination count and rows share filters.
• Verify sorting and nullable relations.
• Reset data between tests.
Two boundaries Two different questions require two different test boundaries
Service unit test Repository integration test TasksService -> FakeTaskRepository PrismaTaskRepository -> PostgreSQL No PostgreSQL required Real migrations + queries
Why both matter A service unit test can pass while a Prisma where clause is wrong. A repository integration test can pass while business policy is wrong. Keep the questions separate.
ORMs do not remove the database. SQL literacy lets you reason about correctness, constraints, query cost, transactions, and the evidence stored in PostgreSQL.
Restate the goal of “Repository Integration Tests with PostgreSQL” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: application intent → SQL statement → query planner → table/index → rows returned. Mark the one boundary this lesson changes.
Inspect the current repository state and record the exact files, route, table, or runtime involved. Avoid creating an abstraction before you can name the existing owner.
Implement the smallest vertical slice. Add one coherent change, run the narrowest verification command, and read the output before continuing.
Connect the slice to TaskFlow’s phase artifact: One TaskFlow aggregate/use case refactored behind a purposeful repository interface with real database integration tests.. Verify behavior from the outside as a user or API client would.
Create one controlled failure that is safe to reproduce. Predict the symptom first, capture evidence, locate the earliest broken boundary, then fix only that cause.
Close the reference and rebuild or explain the core change from memory. Record what you would monitor or test before trusting the same change in production.
SELECT t.id, t.title, u.name AS assignee
FROM tasks AS t
LEFT JOIN users AS u ON u.id = t.assignee_id
WHERE t.workspace_id = $1
ORDER BY t.created_at DESC, t.id DESC;Do not copy this as a finished answer. Predict what each boundary does, type the smallest useful slice, run it, then compare the result with your prediction.
Capture EXPLAIN ANALYZE, row counts, filters, sort keys, and indexes before adding an index.
Inspect join cardinality and constraints; do not hide a modeling bug with DISTINCT until you understand it.
Without copying the final source, create a second small scenario that applies “Repository Integration Tests with PostgreSQL” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Move Prisma-specific selection/query details into the implementation.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.GenericRepository<T> mirroring ORM methods
Predict the symptom before causing the failure. Then locate the earliest boundary where reality diverges from expectation.Why does this responsibility live here, what input does it trust, what output proves success, and what would go wrong if another layer owned it?
If your explanation is vague, repeat the boundary trace before moving on.Close the reference. Reproduce the core idea from memory or explain the exact request/data flow aloud. Then check your diff or notes for accidental shortcuts that bypass validation, authorization, error handling, or verification earned in earlier phases.