title: PHPUnit does not open files without ".php" suffix
body: <p>I decided to use PHPUnit in my project for testing purposes. In order to do that, I installed Composer from Composer's official site(it is Composer of the latest version; I am mentioning that a bit ahead of time so that you can understand that updating Composer will not solve the problem) and installed PHPUnit with the help of Composer in command line. My <code>composer.json</code> looks like this:</p>
  <pre><code>{
      &quot;autoload&quot;: {
          &quot;classmap&quot;: [
              &quot;&quot;
          ]
      },
      &quot;require-dev&quot;: {
          &quot;phpunit/phpunit&quot;: &quot;^9&quot;
      }
  }
  </code></pre>
  <p>I also have <code>phpunit.xml.dist</code>. It looks like this:</p>
  <pre><code>&lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;
  &lt;phpunit bootstrap=&quot;vendor/autoload.php&quot;&gt;
      &lt;testsuites&gt;
          &lt;testsuite name=&quot;Components&quot;&gt;
              &lt;directory suffix=&quot;Test.php&quot;&gt;./tests/components/&lt;/directory&gt;
          &lt;/testsuite&gt;
      &lt;/testsuites&gt;
  &lt;/phpunit&gt;
  </code></pre>
  <p>As you can see from this piece of code, my code in organised in the following manner:</p>
  <pre><code>--folderForClasses
  --anotherFolderForClasses
  --OneMoreFolder
  --vendor
     `--autoload.php
  --tests
     `--components
           `--TokenGeneratorTest.php
  --composer.json
  --phpunit.xml.dist
  </code></pre>
  <p>I <strong>CAN</strong> execute commands like:</p>
  <ol>
  <li><code>vendor\bin\phpunit tests</code></li>
  <li><code>vendor\bin\phpunit tests/components</code></li>
  <li><code>vendor\bin\phpunit tests/components/TokenGeneratorTest.php</code></li>
  <li><code>vendor\bin\phpunit --testsuite Components </code></li>
  </ol>
  <p>Because there is only one test file, all of that results in the following:</p>
  <pre><code>PHPUnit 9.0.0 by Sebastian Bergmann and contributors.
  
  ...                                                                 3 / 3 (100%)
  
  Time: 00:00.066, Memory: 4.00 MB
  
  OK (3 tests, 3 assertions)
  </code></pre>
  <p>However, I <strong>CANNOT</strong> execute command like:</p>
  <ol>
  <li><code>vendor\bin\phpunit TokenGeneratorTest</code></li>
  <li><code>vendor\bin\phpunit tests/components/TokenGeneratorTest</code></li>
  </ol>
  <p>These two commands result in:</p>
  <pre><code>PHPUnit 9.0.0 by Sebastian Bergmann and contributors.
  
  Cannot open file &quot;TokenGeneratorTest&quot;.
  </code></pre>
  <p>And:</p>
  <pre><code>PHPUnit 9.0.0 by Sebastian Bergmann and contributors.
  
  Cannot open file &quot;tests/components/TokenGeneratorTest&quot;.
  </code></pre>
  <p>I have seen in several tutorials that commands like the last two should be working, but for some reason they do not work. What could be the reason for that and how to make it work?</p>
  <p>Thanks a lot in advance.</p>