Upgrade to composer v2.

Author: ADmad

composer.json

@@ -13,9 +13,9 @@
         "php": "^7.2"
     },
     "require-dev": {
-        "composer/composer": "^1.0",
-        "phpunit/phpunit": "~8.5.0",
-        "cakephp/cakephp-codesniffer": "^4.1"
+        "cakephp/cakephp-codesniffer": "^4.1",
+        "composer/composer": "^2.0@dev",
+        "phpunit/phpunit": "~8.5.0"
     },
     "autoload": {
         "psr-4": {
@@ -29,5 +29,10 @@
     },
     "extra": {
         "class": "Cake\\Composer\\Installer\\PluginInstaller"
-    }
+    },
+    "config": {
+        "sort-packages": true
+    },
+    "minimum-stability": "dev",
+    "prefer-stable": true
 }

tests/TestCase/Installer/PluginInstallerTest.php

@@ -7,6 +7,7 @@
 use Composer\Composer;
 use Composer\Package\Package;
 use Composer\Repository\RepositoryManager;
+use Composer\Util\HttpDownloader;
 use PHPUnit\Framework\TestCase;
 
 class PluginInstallerTest extends TestCase
@@ -59,9 +60,13 @@ public function setUp(): void
         $composer->setConfig($config);
 
         $this->io = $this->getMockBuilder('Composer\IO\IOInterface')->getMock();
+
+        $httpDownloader = new HttpDownloader($this->io, $config);
+
         $rm = new RepositoryManager(
             $this->io,
-            $config
+            $config,
+            $httpDownloader
         );
         $composer->setRepositoryManager($rm);