docs: update test naming examples to BDD Given-When-Then

Author: nanotaboada

.github/copilot-instructions.md

@@ -33,7 +33,7 @@ This is a Spring Boot REST API for managing football players, demonstrating mode
 
 - **Classes**: PascalCase (e.g., `PlayersController`, `PlayerDTO`)
 - **Methods/Variables**: camelCase (e.g., `findById`, `squadNumber`)
-- **Test methods**: `method_scenario_outcome` (e.g., `post_squadNumberExists_returnsConflict`)
+- **Test methods**: `givenX_whenY_thenZ` (e.g., `givenSquadNumberExists_whenPost_thenReturnsConflict`)
 
 ### Annotations
 

AGENTS.md

@@ -62,7 +62,7 @@ Dockerfile                        - Container image definition
 - **All tests**: `./mvnw test`
 - **With coverage**: `./mvnw clean test jacoco:report` (view: `open target/site/jacoco/index.html`)
 - **Single test class**: `./mvnw test -Dtest=PlayersControllerTests`
-- **Single test method**: `./mvnw test -Dtest=PlayersControllerTests#getAll_playersExist_returnsOkWithAllPlayers`
+- **Single test method**: `./mvnw test -Dtest=PlayersControllerTests#givenPlayersExist_whenGetAll_thenReturnsOkWithAllPlayers`
 - **Integration tests require**: In-memory SQLite (automatic, no docker needed)
 - **Full CI pipeline locally**: `./mvnw clean install` (compile + test + package + jacoco)