Installation failed for phpunit/phpunit ^6.2

Question

when i run

composer require --dev phpunit/phpunit

i get the following message:

composer require --dev phpunit/phpunit
Using version ^6.2 for phpunit/phpunit
./composer.json has been updated
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
- Installation request for sebastian/object-enumerator (locked at 2.0.1) -> satisfiable by sebastian/object-enumerator[2.0.1].
- phpunit/phpunit 6.2.0 requires sebastian/object-enumerator ^3.0.2 -> satisfiable by sebastian/object-enumerator[3.0.2].
- phpunit/phpunit 6.2.1 requires sebastian/object-enumerator ^3.0.2 -> satisfiable by sebastian/object-enumerator[3.0.2].
- phpunit/phpunit 6.2.2 requires sebastian/object-enumerator ^3.0.2 -> satisfiable by sebastian/object-enumerator[3.0.2].
- phpunit/phpunit 6.2.3 requires sebastian/object-enumerator ^3.0.2 -> satisfiable by sebastian/object-enumerator[3.0.2].
- Conclusion: don't install sebastian/object-enumerator 3.0.2
- Installation request for phpunit/phpunit ^6.2 -> satisfiable by phpunit/phpunit[6.2.0, 6.2.1, 6.2.2, 6.2.3].

Installation failed, reverting ./composer.json to its original content.

Here is my composer json file:

"require": {
  "php": "^7.0",
  "laravel/framework": "^5.4",
  "guzzlehttp/guzzle": "^6.3",
  "symfony/psr-http-message-bridge": "^1.0",
  "mcamara/laravel-localization": "^1.2",
  "laravelcollective/html": "^5.4",
  "laravel/socialite": "^3.0",
  "yajra/laravel-datatables-oracle": "^7.9"
},
"require-dev": {
  "fzaninotto/faker": "^1.6",
  "symfony/css-selector": "^3.3",
  "symfony/dom-crawler": "^3.3"
}

I tried to get from version 5.4 above and always get a similar error but with other dependecies, the only version that seems to work is 5.0

Answer 1

Run

$ composer require --dev phpunit/phpunit --update-with-dependencies

See https://getcomposer.org/doc/03-cli.md#require:

--update-with-dependencies: Also update dependencies of the newly required packages.

Note Deleting composer.lock in circumstances like this isn't really the best idea, as it might pull in dependencies that break your code in other places. You really only want to update a specific dependency at a time, rather than update all of them at once.