Add PHPUnit as a development dependency.

Author: Potherca

composer.json

@@ -7,6 +7,11 @@
       "Pdsinterop\\Solid\\Auth\\": "src/"
     }
   },
+  "autoload-dev": {
+    "psr-4": {
+      "Pdsinterop\\Solid\\Auth\\": "tests/unit/"
+    }
+  },
   "config": {
     "bin-dir": "./bin",
     "platform": {
@@ -28,8 +33,11 @@
     "league/oauth2-server": "^8.1"
   },
   "require-dev": {
+    "ext-xdebug": "*",
+    "ext-xml": "*",
     "laminas/laminas-diactoros": "^2.3",
-    "lcobucci/jwt": "^3.3"
+    "lcobucci/jwt": "^3.3",
+    "phpunit/phpunit": "^8.5"
   },
   "type": "library"
 }