Adding tests for the default policy specifying its desired behaviour

src/Composer/DependencyResolver/DefaultPolicy.php

@@ -63,9 +63,8 @@ class DefaultPolicy implements PolicyInterface
         return true;
     }
 
-    public function selectPreferedPackages(Solver $solver, Pool $pool, RepositoryInterface $installed, array $literals)
+    public function selectPreferedPackages(Pool $pool, RepositoryInterface $installed, array $literals)
     {
-        // prefer installed, newest version, recommended, highest priority repository, ...
         $newest = $this->selectNewestPackages($installed, $literals);
 
         $selected = array();

src/Composer/DependencyResolver/PolicyInterface.php

@@ -25,5 +25,5 @@ interface PolicyInterface
     function versionCompare(PackageInterface $a, PackageInterface $b, $operator);
     function findUpdatePackages(Solver $solver, Pool $pool, RepositoryInterface $repo, PackageInterface $package, $allowAll);
     function installable(Solver $solver, Pool $pool, RepositoryInterface $repo, PackageInterface $package);
-    function selectPreferedPackages(Solver $solver, Pool $pool, RepositoryInterface $installed, array $literals);
+    function selectPreferedPackages(Pool $pool, RepositoryInterface $installed, array $literals);
 }

src/Composer/DependencyResolver/Solver.php

@@ -1411,7 +1411,7 @@ class Solver
     private function selectAndInstall($level, array $decisionQueue, $disableRules, Rule $rule)
     {
         // choose best package to install from decisionQueue
-        $literals = $this->policy->selectPreferedPackages($this, $this->pool, $this->installed, $decisionQueue);
+        $literals = $this->policy->selectPreferedPackages($this->pool, $this->installed, $decisionQueue);
 
         $selectedLiteral = array_shift($literals);
 

tests/Composer/Test/DependencyResolver/DefaultPolicyTest.php

@@ -0,0 +1,101 @@
+<?php
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Test\DependencyResolver;
+
+use Composer\Repository\ArrayRepository;
+use Composer\DependencyResolver\DefaultPolicy;
+use Composer\DependencyResolver\Pool;
+use Composer\DependencyResolver\Literal;
+use Composer\Package\MemoryPackage;
+use Composer\Package\Link;
+use Composer\Package\LinkConstraint\VersionConstraint;
+
+class DefaultPolicyTest extends \PHPUnit_Framework_TestCase
+{
+    protected $pool;
+    protected $repo;
+    protected $repoInstalled;
+    protected $request;
+    protected $policy;
+
+    public function setUp()
+    {
+        $this->pool = new Pool;
+        $this->repo = new ArrayRepository;
+        $this->repoInstalled = new ArrayRepository;
+
+        $this->policy = new DefaultPolicy;
+    }
+
+    public function testSelectSingle()
+    {
+        $this->repo->addPackage($packageA = new MemoryPackage('A', '1.0'));
+        $this->pool->addRepository($this->repo);
+
+        $literals = array(new Literal($packageA, true));
+        $expected = array(new Literal($packageA, true));
+
+        $selected = $this->policy->selectPreferedPackages($this->pool, $this->repoInstalled, $literals);
+
+        $this->assertEquals($expected, $selected);
+    }
+
+    public function testSelectNewest()
+    {
+        $this->repo->addPackage($packageA1 = new MemoryPackage('A', '1.0'));
+        $this->repo->addPackage($packageA2 = new MemoryPackage('A', '2.0'));
+        $this->pool->addRepository($this->repo);
+
+        $literals = array(new Literal($packageA1, true), new Literal($packageA2, true));
+        $expected = array(new Literal($packageA2, true));
+
+        $selected = $this->policy->selectPreferedPackages($this->pool, $this->repoInstalled, $literals);
+
+        $this->assertEquals($expected, $selected);
+    }
+
+    public function testSelectInstalled()
+    {
+        $this->repo->addPackage($packageA = new MemoryPackage('A', '1.0'));
+        $this->repoInstalled->addPackage($packageAInstalled = new MemoryPackage('A', '1.0'));
+        $this->pool->addRepository($this->repo);
+        $this->pool->addRepository($this->repoInstalled);
+
+        $literals = array(new Literal($packageA, true), new Literal($packageAInstalled, true));
+        $expected = array(new Literal($packageAInstalled, true));
+
+        $selected = $this->policy->selectPreferedPackages($this->pool, $this->repoInstalled, $literals);
+
+        $this->assertEquals($expected, $selected);
+    }
+
+    public function testSelectLastRepo()
+    {
+        $this->markTestIncomplete();
+
+        $this->repoImportant = new ArrayRepository;
+
+        $this->repo->addPackage($packageA = new MemoryPackage('A', '1.0'));
+        $this->repoImportant->addPackage($packageAImportant = new MemoryPackage('A', '1.0'));
+
+        $this->pool->addRepository($this->repo);
+        $this->pool->addRepository($this->repoImportant);
+
+        $literals = array(new Literal($packageA, true), new Literal($packageAImportant, true));
+        $expected = array(new Literal($packageAImportant, true));
+
+        $selected = $this->policy->selectPreferedPackages($this->pool, $this->repoInstalled, $literals);
+
+        $this->assertEquals($expected, $selected);
+    }
+}