refactor(tests): adopt action-oriented naming convention

Replace BDD-style test names with action-oriented pattern:
test_request_{method}_{resource}_{param_or_context}_response_{outcome}

Test naming changes:
- Rename all 19 integration tests for consistency
- Apply players/player resource distinction (collection vs single)
- Simplify docstrings (single-line, no \"Expected:\" prefix)

Test data updates:
- Update nonexistent_player() to ID 24 (Thiago Almada)
- Use ID 21 (Alejandro Gómez) for deletion test
- Update database: 25 players, ID 24 reserved for creation
- GET /players/ test expects 25 players initially

Documentation:
- Add test naming convention to copilot-instructions.md
- Update AGENTS.md with pattern and examples

Test flow:
- Initial: 25 players (missing ID 24, has ID 21)
- POST creates ID 24 → 26 players
- DELETE removes ID 21 → 25 players

Aligns with multi-language comparison project standards.

Author: nanotaboada

.github/copilot-instructions.md

@@ -129,7 +129,7 @@ class PlayerModel(BaseModel):
 ## Common Issues
 
 1. **SQLAlchemy errors** → Always catch + rollback in services
-2. **Test file** → `test_main.py` excluded from Black (preserves long names)
+2. **Test file** → `test_main.py` excluded from Black
 3. **Database location** → Local: `./storage/`, Docker: `/storage/` (volume)
 4. **Pydantic validation** → Returns 422 (not 400)
 5. **Import order** → stdlib → third-party → local
@@ -155,6 +155,39 @@ curl http://localhost:9000/players    # 200 OK
 - Line length: 88
 - Complexity: ≤10
 
+## Test Naming Convention
+
+Integration tests follow an action-oriented pattern:
+
+**Pattern:**
+```
+test_request_{method}_{resource}_{param_or_context}_response_{outcome}
+```
+
+**Components:**
+- `method` - HTTP verb: `get`, `post`, `put`, `delete`
+- `resource` - `players` (collection) or `player` (single resource)
+- `param_or_context` - Request details: `id_existing`, `squadnumber_nonexistent`, `body_empty`
+- `response` - Literal separator
+- `outcome` - What's asserted: `status_ok`, `status_not_found`, `body_players`, `header_cache_miss`
+
+**Examples:**
+```python
+def test_request_get_players_response_status_ok(client):
+    """GET /players/ returns 200 OK"""
+
+def test_request_get_player_id_existing_response_body_player_match(client):
+    """GET /players/{player_id} with existing ID returns matching player"""
+
+def test_request_post_player_body_empty_response_status_unprocessable(client):
+    """POST /players/ with empty body returns 422 Unprocessable Entity"""
+```
+
+**Docstrings:**
+- Single-line, concise descriptions
+- Complements test name (doesn't repeat)
+- No "Expected:" prefix (redundant)
+
 ## Commit Messages
 
 Follow Conventional Commits format (enforced by commitlint in CI):

AGENTS.md

@@ -71,7 +71,8 @@ async def get_stats(
 1. Tests (`tests/test_main.py`):
 
 ```python
-async def test_given_get_when_player_stats_then_returns_200():
+def test_request_get_player_id_existing_stats_response_status_ok(client):
+    """GET /players/{player_id}/stats with existing ID returns 200 OK"""
     ...
 ```
 
@@ -110,10 +111,22 @@ No Alembic migrations:
 
 ## Testing Strategy
 
+**Naming Pattern:**
+
+```text
+test_request_{method}_{resource}_{param_or_context}_response_{outcome}
+```
+
+- `players` (collection) vs `player` (single resource)
+- Examples: `test_request_get_players_response_status_ok`, `test_request_post_player_body_empty_response_status_unprocessable`
+
+**Guidelines:**
+
 - Use `tests/player_stub.py` for data
 - Test real DB (fixtures handle setup)
 - Cover: happy paths + errors + edges
 - Cache tests: verify `X-Cache` header
+- Docstrings: Single-line, concise, no "Expected:" prefix
 
 ## Planning Tips
 
@@ -130,7 +143,7 @@ No Alembic migrations:
 - `test_main.py`: Excluded from Black
 - SQLAlchemy errors: Catch + rollback in services
 - Validation errors: 422 (not 400)
-- Test file naming: `test_given_when_then` pattern
+- Test naming: `test_request_{method}_{resource}_{context}_response_{outcome}` pattern
 
 ## Cross-Tool Notes
 

storage/players-sqlite3.db

@@ -54,16 +54,16 @@ def nonexistent_player():
     Creates a test stub for a nonexistent (new) Player.
     """
     return Player(
-        id=12,
-        first_name="Leandro",
-        middle_name="Daniel",
-        last_name="Paredes",
-        date_of_birth="1994-06-29T00:00:00.000Z",
-        squad_number=5,
-        position="Defensive Midfield",
-        abbr_position="DM",
-        team="AS Roma",
-        league="Serie A",
+        id=24,
+        first_name="Thiago",
+        middle_name="Ezequiel",
+        last_name="Almada",
+        date_of_birth="2001-04-26T00:00:00.000Z",
+        squad_number=16,
+        position="Attacking Midfield",
+        abbr_position="AM",
+        team="Atlanta United FC",
+        league="Major League Soccer",
         starting11=0,
     )