[TASK] Upgrade to PHPUnit 8 (#973)

Also update the PHPUnit configuration file to use the recommended defaults.

Fixes #942

.gitignore

@@ -21,5 +21,6 @@
 .webprj
 nbproject
 /.php_cs.cache
+/.phpunit.result.cache
 /vendor/
 composer.lock

phive.xml

@@ -3,6 +3,6 @@
   <phar name="phar-io/phive" version="^0.14.4" installed="0.14.4" location="./tools/phive.phar" copy="true"/>
   <phar name="php-cs-fixer" version="^2.16.7" installed="2.16.7" location="./tools/php-cs-fixer.phar" copy="true"/>
   <phar name="phpmd" version="^2.9.1" installed="2.9.1" location="./tools/phpmd.phar" copy="true"/>
-  <phar name="phpunit" version="^7.5.20 || ^9.4.3" installed="7.5.20" location="./tools/phpunit.phar" copy="true"/>
+  <phar name="phpunit" version="^8.5.15 || ^9.5.4" installed="8.5.15" location="./tools/phpunit.phar" copy="true"/>
   <phar name="psalm" version="^4.7.0" installed="4.7.0" location="./tools/psalm.phar" copy="true"/>
 </phive>

phpunit.xml

@@ -1,12 +1,23 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/7.5/phpunit.xsd"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/8.5/phpunit.xsd"
          bootstrap="vendor/autoload.php"
          colors="true"
+         executionOrder="depends,defects"
+         forceCoversAnnotation="true"
+         beStrictAboutCoversAnnotation="true"
+         beStrictAboutOutputDuringTests="true"
+         beStrictAboutTodoAnnotatedTests="true"
          verbose="true">
     <testsuites>
         <testsuite name="default">
-            <directory suffix="Test.php">tests</directory>
+            <directory>tests</directory>
         </testsuite>
     </testsuites>
+
+    <filter>
+        <whitelist processUncoveredFilesFromWhitelist="true">
+            <directory suffix=".php">src</directory>
+        </whitelist>
+    </filter>
 </phpunit>