Every engineer would hope to divide database when running test.
I'll show using another database for phpunit test on Laravel 6 with docker-compose in this article.

STEP

Adding test database on docker-compose
Adding setting for test database in config/database.php
Adding environment at phpunit.xml
Create .env.testing as new env file
Running migration command for test database
Running phpunit

CODES

docer-compose.yml

version: '3' 
services:    
  db:            
    build:   
      context: ./app/mysql
    environment: 
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: hoge
      MYSQL_USER: hoge
      MYSQL_PASSWORD: hoge
    container_name: mydb
    ports: 
      - "3306:3306"
    tty: true
    volumes:
      - ./app/mysql/db_data:/var/lib/mysql
  testdb:            
    build:   
      context: ./app/mysql
    environment: 
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: hoge
      MYSQL_USER: hoge
      MYSQL_PASSWORD: hoge
    container_name: testdb
    ports: 
      - "3307:3306"
    tty: true
    volumes: 
      - ./app/mysql/testdb_data:/var/lib/mysql
  web:
    ...

config/database.php

    ...

    'connections' => [

       ... 

       'mysql' => [
            ...
        ],  
                                                                                                                                                                                                              
        'mysql_testing' => [
            ...
            'host' => 'testdb',
            ...
        ],

phpunit.xml

<?xml version="1.0" encoding="UTF-8"?>                                    
    ...
    <php>                                                                 
        <env name="APP_ENV" value="testing" force="true"/> 
        <env name="DB_CONNECTION" value="mysql_testing" force="true"/> 
        ... 
    </php>                                                                
</phpunit>

.env.testing

APP_ENV=test
APP_KEY=[YOURKEY]
APP_DEBUG=true

$ php artisan:migrate database=mysql_testing
$ ./vendor/bin/phpunit