Resolve "Backend: Unit tests for service layer and business logic"

Closes #19 (closed)

MR: Add Comprehensive Testing Suite for Backend Services & API

Summary

This Merge Request introduces a complete testing infrastructure for the EHRS FastAPI backend. It establishes a tests/ directory structure mirroring the application layout, configures global fixtures for database isolation, and includes unit/integration tests for critical business logic across Services, Models, and API layers.

Key Changes

1. Testing Infrastructure (tests/conftest.py)

• Dedicated Test Database: Configured to use a separate PostgreSQL database (ehrs_test) to prevent data pollution in development/production DBs.
• Transactional Rollback: Implemented a db_session fixture that wraps every test in a transaction and rolls it back upon completion, ensuring a clean state for every test.
• FastAPI Dependency Override: Overrides get_db to inject the test session into API routes during integration testing.

2. Service Layer Tests (tests/test_services/)

Added unit tests for core business logic, covering:

• Doctor Service: Creation logic (linking User+Doctor) and patient queue assignment.
• Medical Camp Service: Role-based signup logic (ensuring Admins sign up as Coordinators, not Volunteers).
• Medicine Service: Inventory management, stock deduction, and error handling for insufficient stock.
• Consultation Queue: Wait time calculation algorithms and valid status transition enforcement.
• User Service: Idempotency of role assignment (preventing duplicate roles).
• Patient Service: User reconciliation (linking new patients to existing users) and camp registration rules.

3. Model Integrity Tests (tests/test_models/)

• Visit Details: Validated add_status logic to enforce strict workflow dependencies (e.g., vitals cannot be added before entry).

4. API Integration Tests (tests/test_api/)

• Patient Routes: Verified endpoints for creating and retrieving patients, ensuring Pydantic validation and correct HTTP status codes (201 vs 404).

Files Added

• tests/conftest.py
• tests/test_services/test_doctor.py
• tests/test_services/test_medical_camp.py
• tests/test_services/test_medicine.py
• tests/test_services/test_consultation_queue.py
• tests/test_services/test_user.py
• tests/test_services/test_patient.py
• tests/test_services/test_patient_consultation.py
• tests/test_models/test_visit.py
• tests/test_api/test_patient_routes.py

How to Test

Prerequisites

Ensure you have a PostgreSQL instance running and the test dependencies installed:

[pip install pytest pytest-mock httpx pytest-cov]

Database Setup

Create the dedicated test database in your PostgreSQL instance

Running the Tests

Execute the full suite from the project root:

Run all tests with verbose output

python3 -m pytest -v

Run with coverage report

python3 -m pytest -v --cov=app tests/

Checklist

[] Global fixtures for DB isolation created.

[] Critical path service logic covered.

[] Database model constraints verified.

[] API integration tests added.

[] Local tests passing.