Add a mocked GitHub repository to streamline testing

tests/MockRepository.php

@@ -0,0 +1,33 @@
+<?php declare(strict_types=1);
+
+namespace ins0\GitHub;
+
+use Generator;
+
+/**
+ * Mocks responses from GitHub's API. Used for testing purposes only.
+ */
+final class MockRepository extends Repository
+{
+    public function __construct(string $repository = '', string $token = null)
+    {
+        $this->releases = [];
+        $this->issues = [];
+        $this->issueEvents = [];
+    }
+
+    public function getReleases(array $params = []): Generator
+    {
+        yield from $this->releases;
+    }
+
+    public function getIssues(array $params = []): Generator
+    {
+        yield from $this->issues;
+    }
+
+    public function getIssueEvents(int $number): Generator
+    {
+        yield from $this->issueEvents[$number];
+    }
+}