Document test organization and add Cursor workflow rules.

Record the one-to-one unit test file convention in README and add rules for test placement and copy-ready PR text after first push.

Co-authored-by: Cursor <cursoragent@cursor.com>

.cursor/rules/pr-after-first-push.mdc

@@ -0,0 +1,58 @@
+---
+description: After first branch push, provide copy-ready PR title and body
+alwaysApply: true
+---
+
+# PR Title and Comment After First Push
+
+The user creates pull requests manually. After the **first push** of a feature branch to remote in a session, always end your response with a copy-ready PR title and PR comment.
+
+## When to provide it
+
+- After the first successful `git push` (or `git push -u origin <branch>`) for a branch in the current task
+- Do **not** create the PR with `gh pr create` unless explicitly asked
+- On later pushes to the same branch, only repeat if the user asks or the change set meaningfully updates what the PR should say
+
+## PR title
+
+- Use a fitting version-bump prefix when changes touch `python_repositories/`:
+  - `[patch]` or `[fix]` — bug fix
+  - `[minor]` or `[feat]` — new feature
+  - `[major]` or `[breaking]` — breaking change
+- Docs-, CI-, or test-only changes: no prefix required
+- Keep the title concise and descriptive
+
+## PR comment format
+
+Provide two separate fenced code blocks the user can copy directly:
+
+1. **PR title** — single line in a code block
+2. **PR comment** — body with `## Summary` and `## Test plan` sections, checklist items reflecting what was actually run
+
+Example structure:
+
+````
+PR title:
+
+```
+[minor] Short description of the change
+```
+
+PR comment:
+
+```
+## Summary
+
+- Bullet points of what changed and why
+
+## Test plan
+
+- [x] Commands or checks that were run
+```
+````
+
+## Notes
+
+- Match the repo PR template ([`.gitea/PULL_REQUEST_TEMPLATE.md`](.gitea/PULL_REQUEST_TEMPLATE.md))
+- Be accurate: only mark test-plan items done if they were run
+- Keep prose clear; the user copies this verbatim into Gitea

.cursor/rules/test-organization.mdc

@@ -0,0 +1,31 @@
+---
+description: Unit test file naming and placement conventions
+globs: tests/**/*.py
+alwaysApply: false
+---
+
+# Test Organization
+
+Unit tests use a one-to-one mapping between source modules and test files.
+
+## Naming
+
+- `python_repositories/<path>/<module>.py` → `tests/unit/<module>_test.py`
+- Test files must end with `_test.py` (enforced by pre-commit `name-tests-test`)
+
+## Placement
+
+- Add tests to the existing `*_test.py` for the module under test
+- Do not create cross-cutting test files (e.g. `structural_typing_test.py`); colocate with the relevant interface/adapter/config test file
+- Shared fixtures → `tests/conftest.py`
+- Module-specific helper classes → the matching test file
+
+## Examples
+
+```
+json_repository_interface.py  →  tests/unit/json_repository_interface_test.py
+redis_adapter.py              →  tests/unit/redis_adapter_test.py
+redis_config.py               →  tests/unit/redis_config_test.py
+```
+
+Integration tests live under `tests/integration/<backend>/` with the same `_test.py` suffix.

README.md

@@ -174,6 +174,15 @@ uv run pytest -v                                      # full suite (requires Doc
 
 Integration tests are marked with `@pytest.mark.integration` and require Docker (testcontainers). Backend-specific markers (`needs_redis`, `needs_minio`) let you run only the containers a test module needs. Run unit tests alone for quick local feedback.
 
+### Test organization
+
+Unit tests live in `tests/unit/` and follow a one-to-one naming convention: `<module>_test.py` tests `python_repositories/<module path>.py`. Examples:
+
+- `json_repository_interface.py` → `tests/unit/json_repository_interface_test.py`
+- `redis_adapter.py` → `tests/unit/redis_adapter_test.py`
+
+Add new tests to the existing file for that module rather than creating cross-cutting test files. Shared fixtures belong in `tests/conftest.py`; module-specific helpers may live in the matching test file.
+
 ### CI base image
 
 Gitea Actions jobs use a pre-built image (`python-repositories-ci`) with Python 3.12,