activate() public method

Makes composer and io available because they are needed in the addKey method.
public activate ( Composer\Composer $composer, Composer\IO\IOInterface $io )
$composer Composer\Composer The composer object
$io Composer\IO\IOInterface Not used
 public function testPreferKeyFromEnv()
 {
     // The key that should be available in the .env file
     $fileKey = 'DOT_ENV_KEY';
     $key = 'ENV_KEY';
     // Make key available in the .env file
     file_put_contents(getcwd() . DIRECTORY_SEPARATOR . '.env', self::KEY_ENV_VARIABLE . '=' . $fileKey);
     // Make key available in the ENVIRONMENT
     putenv(self::KEY_ENV_VARIABLE . '=' . $key);
     // Mock a RemoteFilesystem
     $rfs = $this->getMockBuilder('Composer\\Util\\RemoteFilesystem')->disableOriginalConstructor()->setMethods(['getOptions', 'isTlsDisabled'])->getMock();
     $rfs->expects($this->once())->method('getOptions')->willReturn([]);
     $rfs->expects($this->once())->method('isTlsDisabled')->willReturn(true);
     // Mock Config
     $config = $this->getMockBuilder('Composer\\Config')->getMock();
     // Mock Composer
     $composer = $this->getMockBuilder('Composer\\Composer')->setMethods(['getConfig'])->getMock();
     $composer->expects($this->once())->method('getConfig')->willReturn($config);
     // Mock IOInterface
     $io = $this->getMockBuilder('Composer\\IO\\IOInterface')->getMock();
     // Mock an Event
     $event = $this->getMockBuilder('Composer\\Plugin\\PreFileDownloadEvent')->disableOriginalConstructor()->setMethods(['getProcessedUrl', 'getRemoteFilesystem', 'setRemoteFilesystem'])->getMock();
     $event->expects($this->once())->method('getProcessedUrl')->willReturn(self::REPO_URL);
     $event->expects($this->once())->method('getRemoteFilesystem')->willReturn($rfs);
     $event->expects($this->once())->method('setRemoteFilesystem')->with($this->callback(function ($rfs) use($key) {
         $this->assertAttributeContains("&k={$key}", 'acfFileUrl', $rfs);
         return true;
     }));
     // Call addKey
     $plugin = new Plugin();
     $plugin->activate($composer, $io);
     $plugin->addKey($event);
 }