diff --git a/src/Composer/Factory.php b/src/Composer/Factory.php
index 4fabbe455..1da6c30da 100644
--- a/src/Composer/Factory.php
+++ b/src/Composer/Factory.php
@@ -16,6 +16,7 @@ use Composer\Config\JsonConfigSource;
 use Composer\Json\JsonFile;
 use Composer\IO\IOInterface;
 use Composer\Package\Archiver;
+use Composer\Package\Version\VersionGuesser;
 use Composer\Repository\RepositoryManager;
 use Composer\Repository\WritableRepositoryInterface;
 use Composer\Util\ProcessExecutor;
@@ -264,7 +265,8 @@ class Factory
 
         // load package
         $parser = new VersionParser;
-        $loader  = new Package\Loader\RootPackageLoader($rm, $config, $parser, new ProcessExecutor($io));
+        $guesser = new VersionGuesser(new ProcessExecutor($io), $parser);
+        $loader  = new Package\Loader\RootPackageLoader($rm, $config, $parser, $guesser);
         $package = $loader->load($localConfig);
         $composer->setPackage($package);
 
diff --git a/src/Composer/Package/Loader/RootPackageLoader.php b/src/Composer/Package/Loader/RootPackageLoader.php
index 9c7c436bc..3043a18c5 100644
--- a/src/Composer/Package/Loader/RootPackageLoader.php
+++ b/src/Composer/Package/Loader/RootPackageLoader.php
@@ -16,13 +16,10 @@ use Composer\Package\BasePackage;
 use Composer\Package\AliasPackage;
 use Composer\Config;
 use Composer\Factory;
+use Composer\Package\Version\VersionGuesser;
 use Composer\Package\Version\VersionParser;
 use Composer\Repository\RepositoryManager;
-use Composer\Repository\Vcs\HgDriver;
-use Composer\IO\NullIO;
 use Composer\Util\ProcessExecutor;
-use Composer\Util\Git as GitUtil;
-use Composer\Util\Svn as SvnUtil;
 
 /**
  * ArrayLoader built for the sole purpose of loading the root package
@@ -33,16 +30,28 @@ use Composer\Util\Svn as SvnUtil;
  */
 class RootPackageLoader extends ArrayLoader
 {
+    /**
+     * @var RepositoryManager
+     */
     private $manager;
-    private $config;
-    private $process;
 
-    public function __construct(RepositoryManager $manager, Config $config, VersionParser $parser = null, ProcessExecutor $process = null)
+    /**
+     * @var Config
+     */
+    private $config;
+
+    /**
+     * @var VersionGuesser
+     */
+    private $versionGuesser;
+
+    public function __construct(RepositoryManager $manager, Config $config, VersionParser $parser = null, VersionGuesser $versionGuesser = null)
     {
+        parent::__construct($parser);
+
         $this->manager = $manager;
         $this->config = $config;
-        $this->process = $process ?: new ProcessExecutor();
-        parent::__construct($parser);
+        $this->versionGuesser = $versionGuesser ?: new VersionGuesser(new ProcessExecutor(), $this->versionParser);
     }
 
     public function load(array $config, $class = 'Composer\Package\RootPackage')
@@ -56,7 +65,7 @@ class RootPackageLoader extends ArrayLoader
             if (getenv('COMPOSER_ROOT_VERSION')) {
                 $version = getenv('COMPOSER_ROOT_VERSION');
             } else {
-                $version = $this->guessVersion($config);
+                $version = $this->versionGuesser->guessVersion($this->config, $config);
             }
 
             if (!$version) {
@@ -176,172 +185,4 @@ class RootPackageLoader extends ArrayLoader
 
         return $references;
     }
-
-    private function guessVersion(array $config)
-    {
-        if (function_exists('proc_open')) {
-            $version = $this->guessGitVersion($config);
-            if (null !== $version) {
-                return $version;
-            }
-
-            $version = $this->guessHgVersion($config);
-            if (null !== $version) {
-                return $version;
-            }
-
-            return $this->guessSvnVersion($config);
-        }
-    }
-
-    private function guessGitVersion(array $config)
-    {
-        GitUtil::cleanEnv();
-
-        // try to fetch current version from git tags
-        if (0 === $this->process->execute('git describe --exact-match --tags', $output)) {
-            try {
-                return $this->versionParser->normalize(trim($output));
-            } catch (\Exception $e) {
-            }
-        }
-
-        // try to fetch current version from git branch
-        if (0 === $this->process->execute('git branch --no-color --no-abbrev -v', $output)) {
-            $branches = array();
-            $isFeatureBranch = false;
-            $version = null;
-
-            // find current branch and collect all branch names
-            foreach ($this->process->splitLines($output) as $branch) {
-                if ($branch && preg_match('{^(?:\* ) *(\(no branch\)|\(detached from \S+\)|\S+) *([a-f0-9]+) .*$}', $branch, $match)) {
-                    if ($match[1] === '(no branch)' || substr($match[1], 0, 10) === '(detached ') {
-                        $version = 'dev-'.$match[2];
-                        $isFeatureBranch = true;
-                    } else {
-                        $version = $this->versionParser->normalizeBranch($match[1]);
-                        $isFeatureBranch = 0 === strpos($version, 'dev-');
-                        if ('9999999-dev' === $version) {
-                            $version = 'dev-'.$match[1];
-                        }
-                    }
-                }
-
-                if ($branch && !preg_match('{^ *[^/]+/HEAD }', $branch)) {
-                    if (preg_match('{^(?:\* )? *(\S+) *([a-f0-9]+) .*$}', $branch, $match)) {
-                        $branches[] = $match[1];
-                    }
-                }
-            }
-
-            if (!$isFeatureBranch) {
-                return $version;
-            }
-
-            // try to find the best (nearest) version branch to assume this feature's version
-            $version = $this->guessFeatureVersion($config, $version, $branches, 'git rev-list %candidate%..%branch%');
-
-            return $version;
-        }
-    }
-
-    private function guessHgVersion(array $config)
-    {
-        // try to fetch current version from hg branch
-        if (0 === $this->process->execute('hg branch', $output)) {
-            $branch = trim($output);
-            $version = $this->versionParser->normalizeBranch($branch);
-            $isFeatureBranch = 0 === strpos($version, 'dev-');
-
-            if ('9999999-dev' === $version) {
-                $version = 'dev-'.$branch;
-            }
-
-            if (!$isFeatureBranch) {
-                return $version;
-            }
-
-            // re-use the HgDriver to fetch branches (this properly includes bookmarks)
-            $config = array('url' => getcwd());
-            $driver = new HgDriver($config, new NullIO(), $this->config, $this->process);
-            $branches = array_keys($driver->getBranches());
-
-            // try to find the best (nearest) version branch to assume this feature's version
-            $version = $this->guessFeatureVersion($config, $version, $branches, 'hg log -r "not ancestors(\'%candidate%\') and ancestors(\'%branch%\')" --template "{node}\\n"');
-
-            return $version;
-        }
-    }
-
-    private function guessFeatureVersion(array $config, $version, array $branches, $scmCmdline)
-    {
-        // ignore feature branches if they have no branch-alias or self.version is used
-        // and find the branch they came from to use as a version instead
-        if ((isset($config['extra']['branch-alias']) && !isset($config['extra']['branch-alias'][$version]))
-            || strpos(json_encode($config), '"self.version"')
-        ) {
-            $branch = preg_replace('{^dev-}', '', $version);
-            $length = PHP_INT_MAX;
-
-            $nonFeatureBranches = '';
-            if (!empty($config['non-feature-branches'])) {
-                $nonFeatureBranches = implode('|', $config['non-feature-branches']);
-            }
-
-            foreach ($branches as $candidate) {
-                // return directly, if branch is configured to be non-feature branch
-                if ($candidate === $branch && preg_match('{^(' . $nonFeatureBranches . ')$}', $candidate)) {
-                    return $version;
-                }
-
-                // do not compare against other feature branches
-                if ($candidate === $branch || !preg_match('{^(master|trunk|default|develop|\d+\..+)$}', $candidate, $match)) {
-                    continue;
-                }
-
-                $cmdLine = str_replace(array('%candidate%', '%branch%'), array($candidate, $branch), $scmCmdline);
-                if (0 !== $this->process->execute($cmdLine, $output)) {
-                    continue;
-                }
-
-                if (strlen($output) < $length) {
-                    $length = strlen($output);
-                    $version = $this->versionParser->normalizeBranch($candidate);
-                    if ('9999999-dev' === $version) {
-                        $version = 'dev-'.$match[1];
-                    }
-                }
-            }
-        }
-
-        return $version;
-    }
-
-    private function guessSvnVersion(array $config)
-    {
-        SvnUtil::cleanEnv();
-
-        // try to fetch current version from svn
-        if (0 === $this->process->execute('svn info --xml', $output)) {
-            $trunkPath = isset($config['trunk-path']) ? preg_quote($config['trunk-path'], '#') : 'trunk';
-            $branchesPath = isset($config['branches-path']) ? preg_quote($config['branches-path'], '#') : 'branches';
-            $tagsPath = isset($config['tags-path']) ? preg_quote($config['tags-path'], '#') : 'tags';
-
-            $urlPattern = '#<url>.*/('.$trunkPath.'|('.$branchesPath.'|'. $tagsPath .')/(.*))</url>#';
-
-            if (preg_match($urlPattern, $output, $matches)) {
-                if (isset($matches[2]) && ($branchesPath === $matches[2] || $tagsPath === $matches[2])) {
-                    // we are in a branches path
-                    $version = $this->versionParser->normalizeBranch($matches[3]);
-                    if ('9999999-dev' === $version) {
-                        $version = 'dev-'.$matches[3];
-                    }
-
-                    return $version;
-                }
-
-                return $this->versionParser->normalize(trim($matches[1]));
-            }
-        }
-    }
 }
diff --git a/src/Composer/Package/Version/VersionGuesser.php b/src/Composer/Package/Version/VersionGuesser.php
new file mode 100644
index 000000000..98cf216c8
--- /dev/null
+++ b/src/Composer/Package/Version/VersionGuesser.php
@@ -0,0 +1,201 @@
+<?php
+
+namespace Composer\Package\Version;
+
+use Composer\Config;
+use Composer\Repository\Vcs\HgDriver;
+use Composer\IO\NullIO;
+use Composer\Util\Git as GitUtil;
+use Composer\Util\ProcessExecutor;
+use Composer\Util\Svn as SvnUtil;
+
+class VersionGuesser
+{
+    /**
+     * @var ProcessExecutor
+     */
+    private $process;
+
+    /**
+     * @var VersionParser
+     */
+    private $versionParser;
+
+    /**
+     * @param ProcessExecutor $process
+     * @param VersionParser   $versionParser
+     */
+    public function __construct(ProcessExecutor $process, VersionParser $versionParser)
+    {
+        $this->process = $process;
+        $this->versionParser = $versionParser;
+    }
+
+    public function guessVersion(Config $config, array $packageConfig)
+    {
+        if (function_exists('proc_open')) {
+            $version = $this->guessGitVersion($packageConfig);
+            if (null !== $version) {
+                return $version;
+            }
+
+            $version = $this->guessHgVersion($config, $packageConfig);
+            if (null !== $version) {
+                return $version;
+            }
+
+            return $this->guessSvnVersion($packageConfig);
+        }
+    }
+
+    private function guessGitVersion(array $config)
+    {
+        GitUtil::cleanEnv();
+
+        // try to fetch current version from git tags
+        if (0 === $this->process->execute('git describe --exact-match --tags', $output)) {
+            try {
+                return $this->versionParser->normalize(trim($output));
+            } catch (\Exception $e) {
+            }
+        }
+
+        // try to fetch current version from git branch
+        if (0 === $this->process->execute('git branch --no-color --no-abbrev -v', $output)) {
+            $branches = array();
+            $isFeatureBranch = false;
+            $version = null;
+
+            // find current branch and collect all branch names
+            foreach ($this->process->splitLines($output) as $branch) {
+                if ($branch && preg_match('{^(?:\* ) *(\(no branch\)|\(detached from \S+\)|\S+) *([a-f0-9]+) .*$}', $branch, $match)) {
+                    if ($match[1] === '(no branch)' || substr($match[1], 0, 10) === '(detached ') {
+                        $version = 'dev-'.$match[2];
+                        $isFeatureBranch = true;
+                    } else {
+                        $version = $this->versionParser->normalizeBranch($match[1]);
+                        $isFeatureBranch = 0 === strpos($version, 'dev-');
+                        if ('9999999-dev' === $version) {
+                            $version = 'dev-'.$match[1];
+                        }
+                    }
+                }
+
+                if ($branch && !preg_match('{^ *[^/]+/HEAD }', $branch)) {
+                    if (preg_match('{^(?:\* )? *(\S+) *([a-f0-9]+) .*$}', $branch, $match)) {
+                        $branches[] = $match[1];
+                    }
+                }
+            }
+
+            if (!$isFeatureBranch) {
+                return $version;
+            }
+
+            // try to find the best (nearest) version branch to assume this feature's version
+            $version = $this->guessFeatureVersion($config, $version, $branches, 'git rev-list %candidate%..%branch%');
+
+            return $version;
+        }
+    }
+
+    private function guessHgVersion(Config $config, array $packageConfig)
+    {
+        // try to fetch current version from hg branch
+        if (0 === $this->process->execute('hg branch', $output)) {
+            $branch = trim($output);
+            $version = $this->versionParser->normalizeBranch($branch);
+            $isFeatureBranch = 0 === strpos($version, 'dev-');
+
+            if ('9999999-dev' === $version) {
+                $version = 'dev-'.$branch;
+            }
+
+            if (!$isFeatureBranch) {
+                return $version;
+            }
+
+            // re-use the HgDriver to fetch branches (this properly includes bookmarks)
+            $packageConfig = array('url' => getcwd());
+            $driver = new HgDriver($packageConfig, new NullIO(), $config, $this->process);
+            $branches = array_keys($driver->getBranches());
+
+            // try to find the best (nearest) version branch to assume this feature's version
+            $version = $this->guessFeatureVersion($config, $version, $branches, 'hg log -r "not ancestors(\'%candidate%\') and ancestors(\'%branch%\')" --template "{node}\\n"');
+
+            return $version;
+        }
+    }
+
+    private function guessFeatureVersion(array $config, $version, array $branches, $scmCmdline)
+    {
+        // ignore feature branches if they have no branch-alias or self.version is used
+        // and find the branch they came from to use as a version instead
+        if ((isset($config['extra']['branch-alias']) && !isset($config['extra']['branch-alias'][$version]))
+            || strpos(json_encode($config), '"self.version"')
+        ) {
+            $branch = preg_replace('{^dev-}', '', $version);
+            $length = PHP_INT_MAX;
+
+            $nonFeatureBranches = '';
+            if (!empty($config['non-feature-branches'])) {
+                $nonFeatureBranches = implode('|', $config['non-feature-branches']);
+            }
+
+            foreach ($branches as $candidate) {
+                // return directly, if branch is configured to be non-feature branch
+                if ($candidate === $branch && preg_match('{^(' . $nonFeatureBranches . ')$}', $candidate)) {
+                    return $version;
+                }
+
+                // do not compare against other feature branches
+                if ($candidate === $branch || !preg_match('{^(master|trunk|default|develop|\d+\..+)$}', $candidate, $match)) {
+                    continue;
+                }
+
+                $cmdLine = str_replace(array('%candidate%', '%branch%'), array($candidate, $branch), $scmCmdline);
+                if (0 !== $this->process->execute($cmdLine, $output)) {
+                    continue;
+                }
+
+                if (strlen($output) < $length) {
+                    $length = strlen($output);
+                    $version = $this->versionParser->normalizeBranch($candidate);
+                    if ('9999999-dev' === $version) {
+                        $version = 'dev-'.$match[1];
+                    }
+                }
+            }
+        }
+
+        return $version;
+    }
+
+    private function guessSvnVersion(array $config)
+    {
+        SvnUtil::cleanEnv();
+
+        // try to fetch current version from svn
+        if (0 === $this->process->execute('svn info --xml', $output)) {
+            $trunkPath = isset($config['trunk-path']) ? preg_quote($config['trunk-path'], '#') : 'trunk';
+            $branchesPath = isset($config['branches-path']) ? preg_quote($config['branches-path'], '#') : 'branches';
+            $tagsPath = isset($config['tags-path']) ? preg_quote($config['tags-path'], '#') : 'tags';
+
+            $urlPattern = '#<url>.*/('.$trunkPath.'|('.$branchesPath.'|'. $tagsPath .')/(.*))</url>#';
+
+            if (preg_match($urlPattern, $output, $matches)) {
+                if (isset($matches[2]) && ($branchesPath === $matches[2] || $tagsPath === $matches[2])) {
+                    // we are in a branches path
+                    $version = $this->versionParser->normalizeBranch($matches[3]);
+                    if ('9999999-dev' === $version) {
+                        $version = 'dev-'.$matches[3];
+                    }
+
+                    return $version;
+                }
+
+                return $this->versionParser->normalize(trim($matches[1]));
+            }
+        }
+    }
+}
diff --git a/tests/Composer/Test/Package/Loader/RootPackageLoaderTest.php b/tests/Composer/Test/Package/Loader/RootPackageLoaderTest.php
index 2a4d9ccf6..77139f928 100644
--- a/tests/Composer/Test/Package/Loader/RootPackageLoaderTest.php
+++ b/tests/Composer/Test/Package/Loader/RootPackageLoaderTest.php
@@ -15,175 +15,11 @@ namespace Composer\Test\Package\Loader;
 use Composer\Config;
 use Composer\Package\Loader\RootPackageLoader;
 use Composer\Package\BasePackage;
+use Composer\Package\Version\VersionGuesser;
+use Composer\Package\Version\VersionParser;
 
 class RootPackageLoaderTest extends \PHPUnit_Framework_TestCase
 {
-    public function testDetachedHeadBecomesDevHash()
-    {
-        if (!function_exists('proc_open')) {
-            $this->markTestSkipped('proc_open() is not available');
-        }
-
-        $commitHash = '03a15d220da53c52eddd5f32ffca64a7b3801bea';
-
-        $manager = $this->getMockBuilder('\\Composer\\Repository\\RepositoryManager')
-            ->disableOriginalConstructor()
-            ->getMock()
-        ;
-
-        $executor = $this->getMockBuilder('\\Composer\\Util\\ProcessExecutor')
-            ->setMethods(array('execute'))
-            ->disableArgumentCloning()
-            ->disableOriginalConstructor()
-            ->getMock()
-        ;
-
-        $executor
-            ->expects($this->at(0))
-            ->method('execute')
-            ->with('git describe --exact-match --tags')
-            ->willReturn(1)
-        ;
-
-        $self = $this;
-
-        $executor
-            ->expects($this->at(1))
-            ->method('execute')
-            ->willReturnCallback(function ($command, &$output) use ($self, $commitHash) {
-                $self->assertEquals('git branch --no-color --no-abbrev -v', $command);
-                $output = "* (no branch) $commitHash Commit message\n";
-
-                return 0;
-            })
-        ;
-
-        $config = new Config;
-        $config->merge(array('repositories' => array('packagist' => false)));
-        $loader = new RootPackageLoader($manager, $config, null, $executor);
-        $package = $loader->load(array());
-
-        $this->assertEquals("dev-$commitHash", $package->getVersion());
-    }
-
-    public function testTagBecomesVersion()
-    {
-        if (!function_exists('proc_open')) {
-            $this->markTestSkipped('proc_open() is not available');
-        }
-
-        $manager = $this->getMockBuilder('\\Composer\\Repository\\RepositoryManager')
-            ->disableOriginalConstructor()
-            ->getMock()
-        ;
-
-        $executor = $this->getMockBuilder('\\Composer\\Util\\ProcessExecutor')
-            ->setMethods(array('execute'))
-            ->disableArgumentCloning()
-            ->disableOriginalConstructor()
-            ->getMock()
-        ;
-
-        $self = $this;
-
-        $executor
-            ->expects($this->at(0))
-            ->method('execute')
-            ->willReturnCallback(function ($command, &$output) use ($self) {
-                $self->assertEquals('git describe --exact-match --tags', $command);
-                $output = "v2.0.5-alpha2";
-
-                return 0;
-            })
-        ;
-
-        $config = new Config;
-        $config->merge(array('repositories' => array('packagist' => false)));
-        $loader = new RootPackageLoader($manager, $config, null, $executor);
-        $package = $loader->load(array());
-
-        $this->assertEquals("2.0.5.0-alpha2", $package->getVersion());
-    }
-
-    public function testInvalidTagBecomesVersion()
-    {
-        if (!function_exists('proc_open')) {
-            $this->markTestSkipped('proc_open() is not available');
-        }
-
-        $manager = $this->getMockBuilder('\\Composer\\Repository\\RepositoryManager')
-            ->disableOriginalConstructor()
-            ->getMock()
-        ;
-
-        $executor = $this->getMockBuilder('\\Composer\\Util\\ProcessExecutor')
-            ->setMethods(array('execute'))
-            ->disableArgumentCloning()
-            ->disableOriginalConstructor()
-            ->getMock()
-        ;
-
-        $self = $this;
-
-        $executor
-            ->expects($this->at(0))
-            ->method('execute')
-            ->willReturnCallback(function ($command, &$output) use ($self) {
-                $self->assertEquals('git describe --exact-match --tags', $command);
-                $output = "foo-bar";
-
-                return 0;
-            })
-        ;
-
-        $executor
-            ->expects($this->at(1))
-            ->method('execute')
-            ->willReturnCallback(function ($command, &$output) use ($self) {
-                $self->assertEquals('git branch --no-color --no-abbrev -v', $command);
-                $output = "* foo 03a15d220da53c52eddd5f32ffca64a7b3801bea Commit message\n";
-
-                return 0;
-            })
-        ;
-
-        $config = new Config;
-        $config->merge(array('repositories' => array('packagist' => false)));
-        $loader = new RootPackageLoader($manager, $config, null, $executor);
-        $package = $loader->load(array());
-
-        $this->assertEquals("dev-foo", $package->getVersion());
-    }
-
-    public function testNoVersionIsVisibleInPrettyVersion()
-    {
-        $manager = $this->getMockBuilder('\\Composer\\Repository\\RepositoryManager')
-            ->disableOriginalConstructor()
-            ->getMock()
-        ;
-
-        $executor = $this->getMockBuilder('\\Composer\\Util\\ProcessExecutor')
-            ->setMethods(array('execute'))
-            ->disableArgumentCloning()
-            ->disableOriginalConstructor()
-            ->getMock()
-        ;
-
-        $executor
-            ->expects($this->any())
-            ->method('execute')
-            ->willReturn(null)
-        ;
-
-        $config = new Config;
-        $config->merge(array('repositories' => array('packagist' => false)));
-        $loader = new RootPackageLoader($manager, $config, null, $executor);
-        $package = $loader->load(array());
-
-        $this->assertEquals("1.0.0.0", $package->getVersion());
-        $this->assertEquals("No version set (parsed as 1.0.0)", $package->getPrettyVersion());
-    }
-
     protected function loadPackage($data)
     {
         $manager = $this->getMockBuilder('\\Composer\\Repository\\RepositoryManager')
@@ -218,6 +54,37 @@ class RootPackageLoaderTest extends \PHPUnit_Framework_TestCase
         ), $package->getStabilityFlags());
     }
 
+    public function testNoVersionIsVisibleInPrettyVersion()
+    {
+        $manager = $this->getMockBuilder('\\Composer\\Repository\\RepositoryManager')
+            ->disableOriginalConstructor()
+            ->getMock()
+        ;
+
+        $executor = $this->getMockBuilder('\\Composer\\Util\\ProcessExecutor')
+            ->setMethods(array('execute'))
+            ->disableArgumentCloning()
+            ->disableOriginalConstructor()
+            ->getMock()
+        ;
+
+        $executor
+            ->expects($this->any())
+            ->method('execute')
+            ->willReturn(null)
+        ;
+
+        $config = new Config;
+        $config->merge(array('repositories' => array('packagist' => false)));
+        $loader = new RootPackageLoader($manager, $config, null, new VersionGuesser($executor, new VersionParser()));
+        $package = $loader->load(array());
+
+        $this->assertEquals("1.0.0.0", $package->getVersion());
+        $this->assertEquals("No version set (parsed as 1.0.0)", $package->getPrettyVersion());
+    }
+
+
+
     public function testFeatureBranchPrettyVersion()
     {
         if (!function_exists('proc_open')) {
@@ -272,7 +139,7 @@ class RootPackageLoaderTest extends \PHPUnit_Framework_TestCase
 
         $config = new Config;
         $config->merge(array('repositories' => array('packagist' => false)));
-        $loader = new RootPackageLoader($manager, $config, null, $executor);
+        $loader = new RootPackageLoader($manager, $config, null, new VersionGuesser($executor, new VersionParser()));
         $package = $loader->load(array('require' => array('foo/bar' => 'self.version')));
 
         $this->assertEquals("dev-master", $package->getPrettyVersion());
@@ -321,7 +188,7 @@ class RootPackageLoaderTest extends \PHPUnit_Framework_TestCase
 
         $config = new Config;
         $config->merge(array('repositories' => array('packagist' => false)));
-        $loader = new RootPackageLoader($manager, $config, null, $executor);
+        $loader = new RootPackageLoader($manager, $config, null, new VersionGuesser($executor, new VersionParser()));
         $package = $loader->load(array('require' => array('foo/bar' => 'self.version'), "non-feature-branches" => array("latest-.*")));
 
         $this->assertEquals("dev-latest-production", $package->getPrettyVersion());
diff --git a/tests/Composer/Test/Package/Version/VersionGuesserTest.php b/tests/Composer/Test/Package/Version/VersionGuesserTest.php
new file mode 100644
index 000000000..7891d1062
--- /dev/null
+++ b/tests/Composer/Test/Package/Version/VersionGuesserTest.php
@@ -0,0 +1,158 @@
+<?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\Package\Version;
+
+use Composer\Config;
+use Composer\Package\Loader\RootPackageLoader;
+use Composer\Package\Version\VersionGuesser;
+use Composer\Package\Version\VersionParser;
+
+class VersionGuesserTest extends \PHPUnit_Framework_TestCase
+{
+    public function testDetachedHeadBecomesDevHash()
+    {
+        if (!function_exists('proc_open')) {
+            $this->markTestSkipped('proc_open() is not available');
+        }
+
+        $commitHash = '03a15d220da53c52eddd5f32ffca64a7b3801bea';
+
+        $manager = $this->getMockBuilder('\\Composer\\Repository\\RepositoryManager')
+            ->disableOriginalConstructor()
+            ->getMock()
+        ;
+
+        $executor = $this->getMockBuilder('\\Composer\\Util\\ProcessExecutor')
+            ->setMethods(array('execute'))
+            ->disableArgumentCloning()
+            ->disableOriginalConstructor()
+            ->getMock()
+        ;
+
+        $executor
+            ->expects($this->at(0))
+            ->method('execute')
+            ->with('git describe --exact-match --tags')
+            ->willReturn(1)
+        ;
+
+        $self = $this;
+
+        $executor
+            ->expects($this->at(1))
+            ->method('execute')
+            ->willReturnCallback(function ($command, &$output) use ($self, $commitHash) {
+                $self->assertEquals('git branch --no-color --no-abbrev -v', $command);
+                $output = "* (no branch) $commitHash Commit message\n";
+
+                return 0;
+            })
+        ;
+
+        $config = new Config;
+        $config->merge(array('repositories' => array('packagist' => false)));
+        $guesser = new VersionGuesser($executor, new VersionParser());
+        $version = $guesser->guessVersion($config, []);
+
+        $this->assertEquals("dev-$commitHash", $version);
+    }
+
+    public function testTagBecomesVersion()
+    {
+        if (!function_exists('proc_open')) {
+            $this->markTestSkipped('proc_open() is not available');
+        }
+
+        $manager = $this->getMockBuilder('\\Composer\\Repository\\RepositoryManager')
+            ->disableOriginalConstructor()
+            ->getMock()
+        ;
+
+        $executor = $this->getMockBuilder('\\Composer\\Util\\ProcessExecutor')
+            ->setMethods(array('execute'))
+            ->disableArgumentCloning()
+            ->disableOriginalConstructor()
+            ->getMock()
+        ;
+
+        $self = $this;
+
+        $executor
+            ->expects($this->at(0))
+            ->method('execute')
+            ->willReturnCallback(function ($command, &$output) use ($self) {
+                $self->assertEquals('git describe --exact-match --tags', $command);
+                $output = "v2.0.5-alpha2";
+
+                return 0;
+            })
+        ;
+
+        $config = new Config;
+        $config->merge(array('repositories' => array('packagist' => false)));
+        $guesser = new VersionGuesser($executor, new VersionParser());
+        $version = $guesser->guessVersion($config, []);
+
+        $this->assertEquals("2.0.5.0-alpha2", $version);
+    }
+
+    public function testInvalidTagBecomesVersion()
+    {
+        if (!function_exists('proc_open')) {
+            $this->markTestSkipped('proc_open() is not available');
+        }
+
+        $manager = $this->getMockBuilder('\\Composer\\Repository\\RepositoryManager')
+            ->disableOriginalConstructor()
+            ->getMock()
+        ;
+
+        $executor = $this->getMockBuilder('\\Composer\\Util\\ProcessExecutor')
+            ->setMethods(array('execute'))
+            ->disableArgumentCloning()
+            ->disableOriginalConstructor()
+            ->getMock()
+        ;
+
+        $self = $this;
+
+        $executor
+            ->expects($this->at(0))
+            ->method('execute')
+            ->willReturnCallback(function ($command, &$output) use ($self) {
+                $self->assertEquals('git describe --exact-match --tags', $command);
+                $output = "foo-bar";
+
+                return 0;
+            })
+        ;
+
+        $executor
+            ->expects($this->at(1))
+            ->method('execute')
+            ->willReturnCallback(function ($command, &$output) use ($self) {
+                $self->assertEquals('git branch --no-color --no-abbrev -v', $command);
+                $output = "* foo 03a15d220da53c52eddd5f32ffca64a7b3801bea Commit message\n";
+
+                return 0;
+            })
+        ;
+
+        $config = new Config;
+        $config->merge(array('repositories' => array('packagist' => false)));
+        $guesser = new VersionGuesser($executor, new VersionParser());
+        $version = $guesser->guessVersion($config, []);
+
+        $this->assertEquals("dev-foo", $version);
+    }
+}