title: Unable to install phpunit ,Conclusion: don't install phpunit/phpunit 6.5.8
body: <p>I have php 7.0.29 version installed on my vagrant setup on windows 10.</p>
  
  <p>When I run following command </p>
  
  <pre><code>composer require --dev phpunit/phpunit
  </code></pre>
  
  <p>I get errors as mentioned</p>
  
  <pre><code>Using version ^6.5 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
      - Conclusion: don't install phpunit/phpunit 6.5.8
      - Conclusion: don't install phpunit/phpunit 6.5.7
      - Conclusion: don't install phpunit/phpunit 6.5.6
      - Conclusion: don't install phpunit/phpunit 6.5.5
      - Conclusion: don't install phpunit/phpunit 6.5.4
      - Conclusion: don't install phpunit/phpunit 6.5.3
      - Conclusion: don't install phpunit/phpunit 6.5.2
      - Conclusion: don't install phpunit/phpunit 6.5.1
      - phpunit/dbunit 2.0.3 conflicts with phpunit/phpunit[6.5.0].
      - phpunit/phpunit 6.5.0 conflicts with phpunit/dbunit[2.0.3].
      - phpunit/phpunit 6.5.0 conflicts with phpunit/dbunit[2.0.3].
      - Installation request for phpunit/phpunit ^6.5 -&gt; satisfiable by phpunit/phpunit[6.5.0, 6.5.1, 6.5.2, 6.5.3, 6.5.4, 6.5.5, 6.5.6, 6.5.7, 6.5.8].
      - Installation request for phpunit/dbunit (locked at 2.0.3, required as ^2.0) -&gt; satisfiable by phpunit/dbunit[2.0.3].
  </code></pre>
  
  <p>My composer.json file has following code</p>
  
  <pre><code>{
      "name": "tsawler/acme",
      "authors": [
          {
              "name": "xyz",
              "email": "xyz@example.com"
          }
      ],
      "require": {
          "filp/whoops": "2.0.*",
          "vlucas/phpdotenv": "~1.1",
          "illuminate/database": "5.1.*",
          "altorouter/altorouter": "1.1.0",
          "respect/validation": "~1.0",
          "duncan3dc/blade": "2.2.*",
          "robmorgan/phinx": "^0.4.5",
          "symfony/var-dumper": "^2.7",
          "cocur/slugify": "^1.2",
          "swiftmailer/swiftmailer": "^5.4",
          "kunststube/csrfp": "^0.1.0",
          "sunra/php-simple-html-dom-parser": "v1.5.0",
          "rdlowrey/auryn": "1.1.*",
          "fabpot/goutte": "^3.1"
      },
      "autoload": {
        "psr-4": { "Acme\\": "src/" }
      },
      "require-dev": {
          "phpunit/phpunit": "^5.1",
          "phpunit/php-invoker": "^1.1",
          "phpunit/dbunit": "^2.0"
      }
  }
  </code></pre>
  
  <p>How do I fix it?</p>