diff --git a/src/ResourceHelper.php b/src/ResourceHelper.php
index 2891213..dbe188c 100644
--- a/src/ResourceHelper.php
+++ b/src/ResourceHelper.php
@@ -28,6 +28,7 @@ trait ResourceHelper
 {
     /**
      * @var resource
+     * @psalm-var resource|closed-resource
      */
     private $resource;
 
diff --git a/tests/TestReader.php b/src/TestReader.php
similarity index 90%
rename from tests/TestReader.php
rename to src/TestReader.php
index d52eaea..a355889 100644
--- a/tests/TestReader.php
+++ b/src/TestReader.php
@@ -17,6 +17,9 @@
 
 /**
  * Class TestReader.
+ *
+ * This reader is designed to be used in tests, as it is somewhat complex to
+ * mock methods that take arguments passed by reference.
  */
 final class TestReader implements ReadSeeker
 {
diff --git a/tests/.gitignore b/tests/.gitignore
new file mode 100644
index 0000000..e69de29