feat(tests): implemented local test DB container for isolation

7project/backend/docker-compose.test.yml

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+version: "3.9"
+services:
+  mariadb:
+    image: mariadb:11.4
+    container_name: test-mariadb
+    environment:
+      MARIADB_ROOT_PASSWORD: rootpw
+      MARIADB_DATABASE: group_project
+      MARIADB_USER: appuser
+      MARIADB_PASSWORD: apppass
+    ports:
+      - "3307:3306"  # host:container (use 3307 on host to avoid conflicts)
+    healthcheck:
+      test: ["CMD", "mariadb-admin", "ping", "-h", "127.0.0.1", "-u", "root", "-prootpw", "--silent"]
+      interval: 5s
+      timeout: 2s
+      retries: 20
+    # Truly ephemeral, fast storage (removed when container stops)
+    tmpfs:
+      - /var/lib/mysql

7project/backend/test-with-ephemeral-mariadb.sh

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+#!/usr/bin/env bash
+set -euo pipefail
+
+# Run tests against a disposable local MariaDB on host port 3307 using Docker Compose.
+# Requirements: Docker, docker compose plugin, Python, Alembic, pytest.
+# Usage:
+#   chmod +x ./test-with-ephemeral-mariadb.sh
+#   ./test-with-ephemeral-mariadb.sh
+#
+# This script will:
+# 1) Start a MariaDB 11.4 container (ephemeral storage, port 3307)
+# 2) Wait until it's healthy
+# 3) Export env vars expected by the app (DATABASE_URL etc.)
+# 4) Run Alembic migrations
+# 5) Run pytest
+# 6) Tear everything down (containers and tmpfs data)
+
+COMPOSE_FILE="docker-compose.test.yml"
+SERVICE_NAME="mariadb"
+CONTAINER_NAME="test-mariadb"
+
+if ! command -v docker >/dev/null 2>&1; then
+  echo "Docker is required but not found in PATH" >&2
+  exit 1
+fi
+if ! docker compose version >/dev/null 2>&1; then
+  echo "Docker Compose V2 plugin is required (docker compose)" >&2
+  exit 1
+fi
+
+# Bring up the DB
+echo "Starting MariaDB (port 3307) with docker compose..."
+docker compose -f "$COMPOSE_FILE" up -d
+
+# Ensure we clean up on exit
+cleanup() {
+  echo "\nTearing down docker compose stack..."
+  docker compose -f "$COMPOSE_FILE" down -v || true
+}
+trap cleanup EXIT
+
+# Wait for healthy container
+echo -n "Waiting for MariaDB to become healthy"
+for i in {1..60}; do
+  status=$(docker inspect -f '{{.State.Health.Status}}' "$CONTAINER_NAME" 2>/dev/null || echo "")
+  if [ "$status" = "healthy" ]; then
+    echo " -> healthy"
+    break
+  fi
+  echo -n "."
+  sleep 1
+  if [ $i -eq 60 ]; then
+    echo "\nMariaDB did not become healthy in time" >&2
+    exit 1
+  fi
+done
+
+# Export env vars for the app/tests (match app/core/db.py expectations)
+export MARIADB_HOST=127.0.0.1
+export MARIADB_PORT=3307
+export MARIADB_DB=group_project
+export MARIADB_USER=appuser
+export MARIADB_PASSWORD=apppass
+export DATABASE_URL="mysql+asyncmy://$MARIADB_USER:$MARIADB_PASSWORD@$MARIADB_HOST:$MARIADB_PORT/$MARIADB_DB"
+export PYTEST_RUN_CONFIG="True"
+
+# Run Alembic migrations then tests
+pushd . >/dev/null
+  echo "Running Alembic migrations..."
+  alembic upgrade head
+
+  echo "Running pytest..."
+  pytest "$@"
+popd >/dev/null
+
+# Cleanup handled by trap