diff --git a/psalm.xml b/psalm.xml
index d62327136..477eb267a 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -18,24 +18,6 @@
         <MisplacedRequiredParam errorLevel="suppress" />
         <NullOperand errorLevel="suppress" />
 
-        <InvalidArgument>
-            <errorLevel type="suppress">
-                <directory name="tests" />
-            </errorLevel>
-        </InvalidArgument>
-
-        <MissingReturnType>
-            <errorLevel type="suppress">
-                <directory name="tests" />
-            </errorLevel>
-        </MissingReturnType>
-
-        <MissingPropertyType>
-            <errorLevel type="suppress">
-                <directory name="tests" />
-            </errorLevel>
-        </MissingPropertyType>
-
         <MixedArgument>
             <errorLevel type="suppress">
                 <directory name="tests" />
diff --git a/src/Psalm/Type/Union.php b/src/Psalm/Type/Union.php
index b14651304..e45e83863 100644
--- a/src/Psalm/Type/Union.php
+++ b/src/Psalm/Type/Union.php
@@ -30,6 +30,9 @@ class Union extends Type
         }
     }
 
+    /**
+     * @return string
+     */
     public function __toString()
     {
         return implode(
diff --git a/tests/ConfigTest.php b/tests/ConfigTest.php
index dc95d0ea6..89c20a7a3 100644
--- a/tests/ConfigTest.php
+++ b/tests/ConfigTest.php
@@ -8,8 +8,6 @@ use Psalm\Config;
 
 class ConfigTest extends PHPUnit_Framework_TestCase
 {
-    protected static $file_filter;
-
     /** @var \Psalm\Checker\ProjectChecker */
     protected $project_checker;
 
@@ -30,11 +28,19 @@ class ConfigTest extends PHPUnit_Framework_TestCase
     {
         return array_filter(
             array_map(
+                /**
+                 * @param string $file_name
+                 * @return string
+                 */
                 function ($file_name) {
                     return substr($file_name, 0, -4);
                 },
                 scandir(dirname(__DIR__) . '/src/Psalm/Issue')
             ),
+            /**
+             * @param string $issue_name
+             * @return bool
+             */
             function ($issue_name) {
                 return !empty($issue_name) && $issue_name !== 'CodeError' && $issue_name !== 'CodeIssue';
             }
@@ -138,6 +144,10 @@ class ConfigTest extends PHPUnit_Framework_TestCase
         $all_possible_handlers = implode(
             ' ',
             array_map(
+                /**
+                 * @param string $issue_name
+                 * @return string
+                 */
                 function ($issue_name) {
                     return '<' . $issue_name . ' errorLevel="suppress" />' . PHP_EOL;
                 },
diff --git a/tests/IncludeTest.php b/tests/IncludeTest.php
index f2aeacd4e..9cbffa572 100644
--- a/tests/IncludeTest.php
+++ b/tests/IncludeTest.php
@@ -13,7 +13,6 @@ class IncludeTest extends PHPUnit_Framework_TestCase
 
     /** @var \Psalm\Checker\ProjectChecker */
     protected $project_checker;
-    protected static $file_filter;
 
     /**
      * @return void
diff --git a/tests/IssueSuppressionTest.php b/tests/IssueSuppressionTest.php
index d6ea86213..f1b5fc877 100644
--- a/tests/IssueSuppressionTest.php
+++ b/tests/IssueSuppressionTest.php
@@ -13,7 +13,6 @@ class IssueSuppressionTest extends PHPUnit_Framework_TestCase
 
     /** @var \Psalm\Checker\ProjectChecker */
     protected $project_checker;
-    protected static $file_filter;
 
     /**
      * @return void
diff --git a/tests/PropertyTypeTest.php b/tests/PropertyTypeTest.php
index 964ea17bf..fb2748f62 100644
--- a/tests/PropertyTypeTest.php
+++ b/tests/PropertyTypeTest.php
@@ -14,7 +14,6 @@ class PropertyTypeTest extends PHPUnit_Framework_TestCase
 
     /** @var \Psalm\Checker\ProjectChecker */
     protected $project_checker;
-    protected static $file_filter;
 
     /**
      * @return void
diff --git a/tests/ScopeTest.php b/tests/ScopeTest.php
index 99208c59d..7688cbf5d 100644
--- a/tests/ScopeTest.php
+++ b/tests/ScopeTest.php
@@ -14,7 +14,6 @@ class ScopeTest extends PHPUnit_Framework_TestCase
 
     /** @var \Psalm\Checker\ProjectChecker */
     protected $project_checker;
-    protected static $file_filter;
 
     /**
      * @return void
@@ -523,8 +522,6 @@ class ScopeTest extends PHPUnit_Framework_TestCase
         echo $a;
         ');
 
-        Config::getInstance()->setIssueHandler('PossiblyUndefinedVariable', self::$file_filter);
-
         $file_checker = new FileChecker('somefile.php', $this->project_checker, $stmts);
         $file_checker->visitAndAnalyzeMethods();
     }