[wip] add tests

tests/ExampleDocumentAccess.php

@@ -0,0 +1,29 @@
+<?php
+
+use IO\Filesystem\File;
+use PDF\Document;
+use PDF\Metadata;
+
+trait ExampleDocumentAccess
+{
+    protected function exampleDocument(?Metadata $metadata = null): Document
+    {
+        return new Document(
+            $this->exampleFile(),
+            $metadata ?? Metadata::empty()
+        );
+    }
+
+    protected function exampleDocumentWithMetadata(array $data): Document
+    {
+        return new Document(
+            $this->exampleFile(),
+            Metadata::fill($data)
+        );
+    }
+
+    protected function exampleFile(): File
+    {
+        return File::fromString(__DIR__ . '/resources/example.pdf');
+    }
+}