laravel migration to 5.6 from 5.5 composer dependency error

Question

I'm trying to upgrade a laravel project to 5.6 from 5.5. I followed the instructions in the documentation

i'm getting this error while running composer update: The error seems to be related to phpunit/phpunit, which I upgraded to ~7.0

onsort git:(master) ✗ composer update Loading composer repositories with package information Updating dependencies (including require-dev) Your requirements could not be resolved to an installable set of packages.

Problem 1 - Conclusion: don't install phpunit/phpunit 7.0.2|install sebastian/comparator 2.1.3 - Conclusion: don't install phpunit/phpunit 7.0.1|install sebastian/comparator 2.1.3 - Conclusion: don't install sebastian/comparator 2.1.3 - phpunit/phpunit 7.0.0 requires sebastian/comparator ^2.1 -> satisfiable by sebastian/comparator[2.1.1, 2.1.0, 2.1.2, 2.1.3]. - sebastian/comparator 2.1.0 requires sebastian/diff ^2.0 -> satisfiable by sebastian/diff[2.0.1]. - sebastian/comparator 2.1.1 requires sebastian/diff ^2.0 -> satisfiable by sebastian/diff[2.0.1]. - sebastian/comparator 2.1.2 requires sebastian/diff ^2.0 -> satisfiable by sebastian/diff[2.0.1]. - sebastian/comparator 2.1.1 requires sebastian/diff ^2.0 -> satisfiable by sebastian/diff[2.0.1]. - Can only install one of: sebastian/diff[3.0.0, 2.0.1]. - Can only install one of: sebastian/diff[3.0.0, 2.0.1]. - phpunit/phpunit 7.0.0 requires sebastian/diff ^3.0 -> satisfiable by sebastian/diff[3.0.0]. - Installation request for phpunit/phpunit ~7.0 -> satisfiable by phpunit/phpunit[7.0.0, 7.0.1, 7.0.2].

composer.json:

 "require": {
        "php": ">=7.1.3",
        "algolia/algoliasearch-client-php": "^1.23",
        "aws/aws-sdk-php": "~3.0",
        "caouecs/laravel-lang": "~3.0",
        "fideloper/proxy": "~4.0",
        "fzaninotto/faker": "~1.4",
        "illuminate/support": "~5.0",
        "intervention/image": "^2.4",
        "laracasts/utilities": "~3.0",
        "laravel/framework": "5.6.*",
        "laravel/horizon": "^1.0",
        "laravel/scout": "~4.0",
        "laravel/tinker": "~1.0",
        "league/flysystem-aws-s3-v3": "~1.0",
        "predis/predis": "^1.1",
        "tightenco/ziggy":"dev-master",
        "ext-gd": "*"
    },
    "require-dev": {
        "filp/whoops": "~2.0",
        "mockery/mockery": "~1.0",
        "phpunit/phpunit": "~7.0",
        "phpspec/phpspec": "~2.0"
    },

Answer 1

I solved this by reinstall all dependencies from scratch :

$ mv vendor/ oldvendor
$ composer install