diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index bb3b94774..e26271845 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -8,10 +8,14 @@
          convertErrorsToExceptions="true"
          convertNoticesToExceptions="true"
          convertWarningsToExceptions="true"
+         strict="false"
          processIsolation="false"
          stopOnFailure="false"
          bootstrap="tests/bootstrap.php"
 >
+    <php>
+        <env name="SYMFONY_DEPRECATIONS_HELPER" value="weak"/>
+    </php>
     <testsuites>
         <testsuite name="Composer Test Suite">
             <directory>./tests/Composer/</directory>
diff --git a/tests/Composer/Test/ApplicationTest.php b/tests/Composer/Test/ApplicationTest.php
index 85ae6840e..18138d399 100644
--- a/tests/Composer/Test/ApplicationTest.php
+++ b/tests/Composer/Test/ApplicationTest.php
@@ -53,7 +53,7 @@ class ApplicationTest extends TestCase
 
         $index = 0;
         $outputMock->expects($this->at($index++))
-            ->method("writeError");
+            ->method("write");
 
         if (extension_loaded('xdebug')) {
             $outputMock->expects($this->at($index++))
diff --git a/tests/Composer/Test/CacheTest.php b/tests/Composer/Test/CacheTest.php
index 50c767752..693753a3e 100644
--- a/tests/Composer/Test/CacheTest.php
+++ b/tests/Composer/Test/CacheTest.php
@@ -105,11 +105,6 @@ class CacheTest extends TestCase
 
     public function testClearCache()
     {
-        $this->finder
-            ->method('removeDirectory')
-            ->with($this->root)
-            ->willReturn(true);
-
         $this->assertTrue($this->cache->clear());
 
         for ($i = 0; $i < 3; $i++) {
diff --git a/tests/Composer/Test/Installer/LibraryInstallerTest.php b/tests/Composer/Test/Installer/LibraryInstallerTest.php
index 772bb05c8..d92ed3309 100644
--- a/tests/Composer/Test/Installer/LibraryInstallerTest.php
+++ b/tests/Composer/Test/Installer/LibraryInstallerTest.php
@@ -35,7 +35,7 @@ class LibraryInstallerTest extends TestCase
         $this->fs = new Filesystem;
 
         $this->composer = new Composer();
-        $this->config = new Config();
+        $this->config = new Config(false);
         $this->composer->setConfig($this->config);
 
         $this->rootDir = $this->getUniqueTmpDirectory();
diff --git a/tests/Composer/Test/Plugin/PluginInstallerTest.php b/tests/Composer/Test/Plugin/PluginInstallerTest.php
index aa1f9ddbb..d56e054fb 100644
--- a/tests/Composer/Test/Plugin/PluginInstallerTest.php
+++ b/tests/Composer/Test/Plugin/PluginInstallerTest.php
@@ -102,7 +102,7 @@ class PluginInstallerTest extends TestCase
         $this->autoloadGenerator = new AutoloadGenerator($dispatcher);
 
         $this->composer = new Composer();
-        $config = new Config();
+        $config = new Config(false);
         $this->composer->setConfig($config);
         $this->composer->setDownloadManager($dm);
         $this->composer->setRepositoryManager($rm);