spring boot container not running because of dependancy on postgres container

I have one postgres container and one spring boot container. I am running both of them using docker-compose.

Below is the docker-compose.yml file:

version: '3'
services:
  backend:
    build:
      context: .
      dockerfile: Dockerfile.dev
    ports:
      - "8080:8080"
    depends_on:
      - postgres-db
    restart: always
    environment:
      SPRING_DATASOURCE_URL: jdbc:postgresql://postgres-db:5432/testDb
      SPRING_DATASOURCE_USERNAME: root
      SPRING_DATASOURCE_PASSWORD: root
  postgres-db:
    working_dir: /home/models
    image: postgres:11.3-alpine
    restart: always
    environment:
      - POSTGRES_USER=root
      - POSTGRES_PASSWORD=root
      - POSTGRES_DB=testDb
    ports:
      - "5432:5432"
    volumes:
      - ./pgdata:/var/lib/postgresql/data
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql

Here's the Dockerfile.dev

FROM maven:3-jdk-8

ENV HOME=/home/usr/app

RUN mkdir -p $HOME

WORKDIR $HOME

ADD pom.xml $HOME

RUN ["/usr/local/bin/mvn-entrypoint.sh", "mvn", "dependency:go-offline"]

ADD . $HOME

RUN ["mvn", "package"]

CMD ["java","-jar","/usr/app/testApp-1.0.0-SNAPSHOT.jar"]

and here's the application.properties file

spring.datasource.url=jdbc:postgresql://postgres-db:5432/testDb
spring.datasource.username=root
spring.datasource.password=root
spring.jpa.hibernate.ddl-auto=validate

but when I run the containers using docker-container up I am getting the error saying the connection to database failed and the container stops.

Edit: I have added the following db-check.sh file for checking the status of db

#!/bin/sh
# wait-for-postgres.sh

set -e

host="$1"
shift
cmd="$@"

until PGPASSWORD="password" psql -h "$host" -U "root" -c '\q'; do
  >&2 echo "Postgres is unavailable - sleeping"
  sleep 1
done


>&2 echo "Postgres is up - executing command"
exec $cmd

and the new Dockerfile.dev looks like:

FROM maven:3-jdk-8

ENV HOME=/home/usr/app

RUN mkdir -p $HOME

WORKDIR $HOME

ADD db-check.sh $HOME

RUN chmod +x db-check.sh

RUN ["./db-check.sh", "postgres-db:5432", "/usr/local/bin/mvn-entrypoint.sh", "mvn", "dependency:go-offline"]

ADD . $HOME

RUN ["mvn", "package"]

CMD ["java","-jar","/usr/app/testApp-1.0.0-SNAPSHOT.jar"]

but for this script to run successfully I need psql installed in the backend container. Is there any other way of checking this because if feel that I am putting a lot of things in this single backend container for the sake of just checking the status of postgres container.