public function testClear()
 {
     $packageFile1 = new PackageFile('vendor/package1');
     $package1 = new Package($packageFile1, '/path1');
     $packageFile2 = new PackageFile('vendor/package2');
     $package2 = new Package($packageFile2, '/path2');
     $rootPackageFile = new RootPackageFile('vendor/root');
     $rootPackage = new RootPackage($rootPackageFile, '/path3');
     $this->collection->add($package1);
     $this->collection->add($rootPackage);
     $this->collection->add($package2);
     $this->collection->clear();
     $this->assertFalse($this->collection->contains('vendor/root'));
     $this->assertFalse($this->collection->contains('vendor/package1'));
     $this->assertFalse($this->collection->contains('vendor/package2'));
     $this->assertTrue($this->collection->isEmpty());
 }