Enhance testing documentation to emphasize the use of embedded/ephemeral Postgres fixtures for tests requiring a database. Update AGENTS.md, README.md, and SKILL.md to reflect this policy and ensure no external DB dependency for standard test runs.

AGENTS.md

@@ -47,4 +47,5 @@ bun run build
 - Add tests when behavior changes.
 - Verify Go tests after backend changes.
 - Verify Bun tests after TS client changes.
+- For DB-required tests, prefer embedded/ephemeral Postgres fixtures over relying on an externally managed database.
 - If CI fails due runner/network infrastructure, keep logs explicit in workflow output.

README.md

@@ -97,3 +97,9 @@ Workflow: `.gitea/workflows/ci.yml`
 
 - `go test ./...`
 - `bun test` in `libs/geo-api-client`
+
+## Testing policy
+
+- Keep fast unit tests as the default (`go test ./...`).
+- If a test requires a real Postgres instance, use embedded/ephemeral Postgres in the test process or test fixture lifecycle.
+- Do not require manually running an external Postgres container for routine test runs.

SKILL.md

@@ -25,6 +25,7 @@ Use this skill when implementing or debugging backend, frontend integration, Typ
    - Update `internal/app/service.go` first.
    - Then wire request/response changes in `internal/http/handlers.go`.
    - Add/update tests in `internal/http/api_test.go`.
+   - If persistence behavior is under test, use embedded/ephemeral Postgres fixtures (no external DB dependency for standard test runs).
 
 2. Frontend integration changes
    - Update TS client first in `libs/geo-api-client/src/`.