diff --git a/tests/Composer/Test/Repository/VcsRepositoryTest.php b/tests/Composer/Test/Repository/VcsRepositoryTest.php
index 5c253d522..6a4113fec 100644
--- a/tests/Composer/Test/Repository/VcsRepositoryTest.php
+++ b/tests/Composer/Test/Repository/VcsRepositoryTest.php
@@ -47,58 +47,65 @@ class VcsRepositoryTest extends \PHPUnit_Framework_TestCase
 
         // init
         $process = new ProcessExecutor;
-        $process->execute('git init', $null);
+        $exec = function ($command) use ($process) {
+            $cwd = getcwd();
+            if ($process->execute($command, $output, $cwd) !== 0) {
+                throw new \RuntimeException('Failed to execute '.$command.': '.$process->getErrorOutput());
+            }
+        };
+
+        $exec('git init');
         touch('foo');
-        $process->execute('git add foo', $null);
-        $process->execute('git commit -m init', $null);
+        $exec('git add foo');
+        $exec('git commit -m init');
 
         // non-composed tag & branch
-        $process->execute('git tag 0.5.0', $null);
-        $process->execute('git branch oldbranch', $null);
+        $exec('git tag 0.5.0');
+        $exec('git branch oldbranch');
 
         // add composed tag & master branch
         $composer = array('name' => 'a/b');
         file_put_contents('composer.json', json_encode($composer));
-        $process->execute('git add composer.json', $null);
-        $process->execute('git commit -m addcomposer', $null);
-        $process->execute('git tag 0.6.0', $null);
+        $exec('git add composer.json');
+        $exec('git commit -m addcomposer');
+        $exec('git tag 0.6.0');
 
         // add feature-a branch
-        $process->execute('git checkout -b feature/a-1.0-B', $null);
+        $exec('git checkout -b feature/a-1.0-B');
         file_put_contents('foo', 'bar feature');
-        $process->execute('git add foo', $null);
-        $process->execute('git commit -m change-a', $null);
+        $exec('git add foo');
+        $exec('git commit -m change-a');
 
         // add version to composer.json
-        $process->execute('git checkout master', $null);
+        $exec('git checkout master');
         $composer['version'] = '1.0.0';
         file_put_contents('composer.json', json_encode($composer));
-        $process->execute('git add composer.json', $null);
-        $process->execute('git commit -m addversion', $null);
+        $exec('git add composer.json');
+        $exec('git commit -m addversion');
 
         // create tag with wrong version in it
-        $process->execute('git tag 0.9.0', $null);
+        $exec('git tag 0.9.0');
         // create tag with correct version in it
-        $process->execute('git tag 1.0.0', $null);
+        $exec('git tag 1.0.0');
 
         // add feature-b branch
-        $process->execute('git checkout -b feature-b', $null);
+        $exec('git checkout -b feature-b');
         file_put_contents('foo', 'baz feature');
-        $process->execute('git add foo', $null);
-        $process->execute('git commit -m change-b', $null);
+        $exec('git add foo');
+        $exec('git commit -m change-b');
 
         // add 1.0 branch
-        $process->execute('git checkout master', $null);
-        $process->execute('git branch 1.0', $null);
+        $exec('git checkout master');
+        $exec('git branch 1.0');
 
         // add 1.0.x branch
-        $process->execute('git branch 1.1.x', $null);
+        $exec('git branch 1.1.x');
 
         // update master to 2.0
         $composer['version'] = '2.0.0';
         file_put_contents('composer.json', json_encode($composer));
-        $process->execute('git add composer.json', $null);
-        $process->execute('git commit -m bump-version', $null);
+        $exec('git add composer.json');
+        $exec('git commit -m bump-version');
 
         chdir($oldCwd);
     }