Backend: Unit tests for service layer and business logic

Issue: Implement Comprehensive Testing Suite for Backend Services & API

Problem Statement

The current EHRS FastAPI backend lacks a standardized testing infrastructure. As the codebase grows (currently 189+ files), the risk of regression bugs increases with every feature addition. Critical business logic—such as patient-user linking, inventory management, and consultation queues—is currently untested automatically.

We need to establish a robust testing framework to ensure data integrity, verify complex business rules, and enable safe refactoring in the future.

Scope

Service functions Business rules Conditional flows Cross-entity logic Edge cases and failure paths

Testing Guidelines

Mock repository/database calls Focus on logic correctness No HTTP or FastAPI routing tests Acceptance Criteria

Goals

1. Establish Testing Infrastructure: Set up pytest with database isolation to ensure tests don't pollute local or production environments.
2. Verify Core Business Logic: Cover the "Happy Paths" and "Edge Cases" for critical services (Patient, Doctor, Medicine, Auth).
3. Ensure Data Integrity: Verify database constraints and complex model methods (e.g., PostgreSQL Arrays).
4. API Validation: Ensure endpoints correctly validate inputs and return appropriate HTTP status codes.

Scope of Work

1. Infrastructure Setup

• Configure pytest and pytest-cov.
• Create tests/conftest.py with global fixtures:
  • setup_test_db: Create/Drop schema for a dedicated _test database.
  • db_session: Handle transactional rollbacks for every test function.
  • client: Override FastAPI get_db dependency for integration tests.

2. Service Layer Unit Tests

Write unit tests for the following critical services:

• Patient Service: Test patient creation, user linking, and duplicate camp registration prevention.
• Doctor Service: Test doctor profile creation and patient queue assignment.
• Medical Camp Service: Test role-based signup logic (Admin -> Coordinator).
• Medicine Service: Test inventory deduction, stock validation, and batch expiry logic.
• Auth Service: Test password hashing, JWT token generation, and OTP validation.
• Consultation Queue Service: Test wait time calculations and status transitions.
• User Service: Test role assignment idempotency.

3. Model Integrity Tests

• PatientVisitDetails: Verify add_status() enforces the correct workflow order (entry -> doctor_assigning -> ...).

4. API Integration Tests

• Patient Routes: Verify GET /patients/{book_no} (404/200) and POST /patients/ (201/422).

Technical Requirements

• Framework: pytest
• Database: PostgreSQL (Must support ARRAY and UUID types).
• Client: httpx / FastAPI TestClient.
• Mocking: pytest-mock (where external calls like SMS/Email are involved).

Acceptance Criteria

• tests/conftest.py is created and correctly handles DB creation/rollback.
• All new tests pass locally using python -m pytest.
• Critical service logic (Patient linking, Inventory updates) has valid test cases.
• Code coverage report is generated successfully.
• No "test pollution" occurs (data created in one test does not persist to another).

Implementation Plan

• Phase 1: Infrastructure & Config (conftest.py).
• Phase 2: Service Layer Logic (The "Brain").
• Phase 3: API Routes (The "Interface").
• Phase 4: Review & Refine Coverage.