Adding a contract for Countable things and Parsers.

src/Countable.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Contracts;
+
+use phpDocumentor\Reflection\Types\Integer;
+
+interface Countable
+{
+  public function count(): int;
+}

src/Mock/Storage/Memory.php

@@ -7,7 +7,7 @@
 
 class Memory implements Storage, BulkRetriever {
 
-  private $storage = [];
+  protected $storage = [];
 
   public function retrieve(string $id): ?string
   {

src/Parser.php

@@ -0,0 +1,16 @@
+<?php
+
+
+namespace Contracts;
+
+
+interface Parser
+{
+  public function feed(string $chunk);
+
+  public function getRecord();
+
+  public function reset();
+
+  public function finish();
+}